Add support for reading YUV4MPEG2 files to ivfenc.
authorTimothy B. Terriberry <tterribe@xiph.org>
Wed, 26 May 2010 22:27:51 +0000 (18:27 -0400)
committerTimothy B. Terriberry <tterribe@xiph.org>
Thu, 3 Jun 2010 00:35:04 +0000 (20:35 -0400)
A large collection of example files may be found at
 http://media.xiph.org/video/derf/
This also fixes a bug in ivfenc for uncompressed IVF input, which previously
 appeared not to skip past the file header the second time it opened the file.
I don't actually have an IVF file with which to test this fix, however.

Change-Id: Id69a1e11a3fa16c4a4fa8944e880bcea090cd52b

AUTHORS
examples.mk
ivfenc.c
y4minput.c [new file with mode: 0644]
y4minput.h [new file with mode: 0644]

diff --git a/AUTHORS b/AUTHORS
index 9686ac1..4ab6881 100644 (file)
--- a/AUTHORS
+++ b/AUTHORS
@@ -2,3 +2,6 @@
 # Name or Organization <email address>
 
 Google Inc.
+The Mozilla Foundation
+Timothy B. Terriberry <tterriberry@mozilla.com>
+The Xiph.Org Foundation
index f05fd81..0054f29 100644 (file)
@@ -19,8 +19,9 @@ ivfdec.SRCS                 += args.c args.h vpx_ports/config.h
 ivfdec.GUID                  = BA5FE66F-38DD-E034-F542-B1578C5FB950
 ivfdec.DESCRIPTION           = Full featured decoder
 UTILS-$(CONFIG_ENCODERS)    += ivfenc.c
-ivfenc.SRCS                 += args.c args.h vpx_ports/config.h
-ivfenc.SRCS                 += vpx_ports/mem_ops.h vpx_ports/mem_ops_aligned.h
+ivfenc.SRCS                 += args.c args.h y4minput.c y4minput.h
+ivfenc.SRCS                 += vpx_ports/config.h vpx_ports/mem_ops.h
+ivfenc.SRCS                 += vpx_ports/mem_ops_aligned.h
 ivfenc.GUID                  = 548DEC74-7A15-4B2B-AFC3-AA102E7C25C1
 ivfenc.DESCRIPTION           = Full featured encoder
 
index 4dc7082..4d96d46 100644 (file)
--- a/ivfenc.c
+++ b/ivfenc.c
@@ -32,6 +32,7 @@
 #include "vpx/vp8cx.h"
 #include "vpx_ports/mem_ops.h"
 #include "vpx_ports/vpx_timer.h"
+#include "y4minput.h"
 
 static const char *exec_name;
 
@@ -217,49 +218,65 @@ vpx_fixed_buf_t stats_get(stats_io_t *stats)
     return stats->buf;
 }
 
+enum video_file_type
+{
+    FILE_TYPE_RAW,
+    FILE_TYPE_IVF,
+    FILE_TYPE_Y4M
+};
+
 #define IVF_FRAME_HDR_SZ (4+8) /* 4 byte size + 8 byte timestamp */
-static int read_frame(FILE *f, vpx_image_t *img, unsigned int is_ivf)
+static int read_frame(FILE *f, vpx_image_t *img, unsigned int file_type,
+                      y4m_input *y4m)
 {
     int plane = 0;
 
-    if (is_ivf)
+    if (file_type == FILE_TYPE_Y4M)
     {
-        char junk[IVF_FRAME_HDR_SZ];
-
-        /* Skip the frame header. We know how big the frame should be. See
-         * write_ivf_frame_header() for documentation on the frame header
-         * layout.
-         */
-        fread(junk, 1, IVF_FRAME_HDR_SZ, f);
+        if (y4m_input_fetch_frame(y4m, f, img) < 0)
+           return 0;
     }
-
-    for (plane = 0; plane < 3; plane++)
+    else
     {
-        unsigned char *ptr;
-        int w = (plane ? (1 + img->d_w) / 2 : img->d_w);
-        int h = (plane ? (1 + img->d_h) / 2 : img->d_h);
-        int r;
-
-        /* Determine the correct plane based on the image format. The for-loop
-         * always counts in Y,U,V order, but this may not match the order of
-         * the data on disk.
-         */
-        switch (plane)
+        if (file_type == FILE_TYPE_IVF)
         {
-        case 1:
-            ptr = img->planes[img->fmt==VPX_IMG_FMT_YV12? VPX_PLANE_V : VPX_PLANE_U];
-            break;
-        case 2:
-            ptr = img->planes[img->fmt==VPX_IMG_FMT_YV12?VPX_PLANE_U : VPX_PLANE_V];
-            break;
-        default:
-            ptr = img->planes[plane];
+            char junk[IVF_FRAME_HDR_SZ];
+
+            /* Skip the frame header. We know how big the frame should be. See
+             * write_ivf_frame_header() for documentation on the frame header
+             * layout.
+             */
+            fread(junk, 1, IVF_FRAME_HDR_SZ, f);
         }
 
-        for (r = 0; r < h; r++)
+        for (plane = 0; plane < 3; plane++)
         {
-            fread(ptr, 1, w, f);
-            ptr += img->stride[plane];
+            unsigned char *ptr;
+            int w = (plane ? (1 + img->d_w) / 2 : img->d_w);
+            int h = (plane ? (1 + img->d_h) / 2 : img->d_h);
+            int r;
+
+            /* Determine the correct plane based on the image format. The for-loop
+             * always counts in Y,U,V order, but this may not match the order of
+             * the data on disk.
+             */
+            switch (plane)
+            {
+            case 1:
+                ptr = img->planes[img->fmt==VPX_IMG_FMT_YV12? VPX_PLANE_V : VPX_PLANE_U];
+                break;
+            case 2:
+                ptr = img->planes[img->fmt==VPX_IMG_FMT_YV12?VPX_PLANE_U : VPX_PLANE_V];
+                break;
+            default:
+                ptr = img->planes[plane];
+            }
+
+            for (r = 0; r < h; r++)
+            {
+                fread(ptr, 1, w, f);
+                ptr += img->stride[plane];
+            }
         }
     }
 
@@ -267,6 +284,20 @@ static int read_frame(FILE *f, vpx_image_t *img, unsigned int is_ivf)
 }
 
 
+unsigned int file_is_y4m(FILE *infile,
+                         y4m_input *y4m)
+{
+    char raw_hdr[4];
+    if (fread(raw_hdr, 1, 4, infile) == 4 &&
+        memcmp(raw_hdr, "YUV4", 4) == 0 &&
+        y4m_input_open(y4m, infile, raw_hdr, 4) >= 0)
+    {
+        return 1;
+    }
+    rewind(infile);
+    return 0;
+}
+
 #define IVF_FILE_HDR_SZ (32)
 unsigned int file_is_ivf(FILE *infile,
                          unsigned int *fourcc,
@@ -568,8 +599,10 @@ int main(int argc, const char **argv_)
     static const int        *ctrl_args_map = NULL;
     int                      verbose = 0, show_psnr = 0;
     int                      arg_use_i420 = 1;
+    int                      arg_have_timebase = 0;
     unsigned long            cx_time = 0;
-    unsigned int             is_ivf, fourcc;
+    unsigned int             file_type, fourcc;
+    y4m_input                y4m;
 
     exec_name = argv_[0];
 
@@ -686,7 +719,10 @@ int main(int argc, const char **argv_)
         else if (arg_match(&arg, &height, argi))
             cfg.g_h = arg_parse_uint(&arg);
         else if (arg_match(&arg, &timebase, argi))
+        {
             cfg.g_timebase = arg_parse_rational(&arg);
+            arg_have_timebase = 1;
+        }
         else if (arg_match(&arg, &error_resilient, argi))
             cfg.g_error_resilient = arg_parse_uint(&arg);
         else if (arg_match(&arg, &lag_in_frames, argi))
@@ -808,10 +844,24 @@ int main(int argc, const char **argv_)
         return EXIT_FAILURE;
     }
 
-    is_ivf = file_is_ivf(infile, &fourcc, &cfg.g_w, &cfg.g_h);
-
-    if (is_ivf)
+    if (file_is_y4m(infile, &y4m))
     {
+        file_type = FILE_TYPE_Y4M;
+        cfg.g_w = y4m.pic_w;
+        cfg.g_h = y4m.pic_h;
+        /* Use the frame rate from the file only if none was specified on the
+         *  command-line.
+         */
+        if (!arg_have_timebase)
+        {
+            cfg.g_timebase.num = y4m.fps_d;
+            cfg.g_timebase.den = y4m.fps_n;
+        }
+        arg_use_i420 = 0;
+    }
+    else if (file_is_ivf(infile, &fourcc, &cfg.g_w, &cfg.g_h))
+    {
+        file_type = FILE_TYPE_IVF;
         switch (fourcc)
         {
         case 0x32315659:
@@ -825,6 +875,8 @@ int main(int argc, const char **argv_)
             return EXIT_FAILURE;
         }
     }
+    else
+        file_type = FILE_TYPE_RAW;
 
     fclose(infile);
 
@@ -869,8 +921,14 @@ int main(int argc, const char **argv_)
         SHOW(kf_max_dist);
     }
 
-    vpx_img_alloc(&raw, arg_use_i420 ? VPX_IMG_FMT_I420 : VPX_IMG_FMT_YV12,
-                  cfg.g_w, cfg.g_h, 1);
+    if (file_type == FILE_TYPE_Y4M)
+        /*The Y4M reader does its own allocation.
+          Just initialize this here to avoid problems if we never read any
+           frames.*/
+        memset(&raw, 0, sizeof(raw));
+    else
+        vpx_img_alloc(&raw, arg_use_i420 ? VPX_IMG_FMT_I420 : VPX_IMG_FMT_YV12,
+                      cfg.g_w, cfg.g_h, 1);
 
     // This was added so that ivfenc will create monotically increasing
     // timestamps.  Since we create new timestamps for alt-reference frames
@@ -894,6 +952,18 @@ int main(int argc, const char **argv_)
             return EXIT_FAILURE;
         }
 
+        /*Skip the file header.*/
+        if (file_type == FILE_TYPE_IVF)
+        {
+            char raw_hdr[IVF_FILE_HDR_SZ];
+            (void)fread(raw_hdr, 1, IVF_FILE_HDR_SZ, infile);
+        }
+        else if(file_type == FILE_TYPE_Y4M)
+        {
+            char buffer[80];
+            (void)fgets(buffer, sizeof(buffer)/sizeof(*buffer) - 1, infile);
+        }
+
         outfile = fopen(out_fn, "wb");
 
         if (!outfile)
@@ -966,7 +1036,7 @@ int main(int argc, const char **argv_)
 
             if (!arg_limit || frames_in < arg_limit)
             {
-                frame_avail = read_frame(infile, &raw, is_ivf);
+                frame_avail = read_frame(infile, &raw, file_type, &y4m);
 
                 if (frame_avail)
                     frames_in++;
diff --git a/y4minput.c b/y4minput.c
new file mode 100644 (file)
index 0000000..f1f50bc
--- /dev/null
@@ -0,0 +1,880 @@
+/*
+ *  Copyright (c) 2010 The VP8 project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license and patent
+ *  grant that can be found in the LICENSE file in the root of the source
+ *  tree. All contributing project authors may be found in the AUTHORS
+ *  file in the root of the source tree.
+ *
+ *  Based on code from the OggTheora software codec source code,
+ *  Copyright (C) 2002-2010 The Xiph.Org Foundation and contributors.
+ */
+#include <stdlib.h>
+#include <string.h>
+#include "y4minput.h"
+
+static int y4m_parse_tags(y4m_input *_y4m,char *_tags){
+  int   got_w;
+  int   got_h;
+  int   got_fps;
+  int   got_interlace;
+  int   got_par;
+  int   got_chroma;
+  char *p;
+  char *q;
+  got_w=got_h=got_fps=got_interlace=got_par=got_chroma=0;
+  for(p=_tags;;p=q){
+    /*Skip any leading spaces.*/
+    while(*p==' ')p++;
+    /*If that's all we have, stop.*/
+    if(p[0]=='\0')break;
+    /*Find the end of this tag.*/
+    for(q=p+1;*q!='\0'&&*q!=' ';q++);
+    /*Process the tag.*/
+    switch(p[0]){
+      case 'W':{
+        if(sscanf(p+1,"%d",&_y4m->pic_w)!=1)return -1;
+        got_w=1;
+      }break;
+      case 'H':{
+        if(sscanf(p+1,"%d",&_y4m->pic_h)!=1)return -1;
+        got_h=1;
+      }break;
+      case 'F':{
+        if(sscanf(p+1,"%d:%d",&_y4m->fps_n,&_y4m->fps_d)!=2){
+          return -1;
+        }
+        got_fps=1;
+      }break;
+      case 'I':{
+        _y4m->interlace=p[1];
+        got_interlace=1;
+      }break;
+      case 'A':{
+        if(sscanf(p+1,"%d:%d",&_y4m->par_n,&_y4m->par_d)!=2){
+          return -1;
+        }
+        got_par=1;
+      }break;
+      case 'C':{
+        if(q-p>16)return -1;
+        memcpy(_y4m->chroma_type,p+1,q-p-1);
+        _y4m->chroma_type[q-p-1]='\0';
+        got_chroma=1;
+      }break;
+      /*Ignore unknown tags.*/
+    }
+  }
+  if(!got_w||!got_h||!got_fps)return -1;
+  if(!got_interlace)_y4m->interlace='?';
+  if(!got_par)_y4m->par_n=_y4m->par_d=0;
+  /*Chroma-type is not specified in older files, e.g., those generated by
+     mplayer.*/
+  if(!got_chroma)strcpy(_y4m->chroma_type,"420");
+  return 0;
+}
+
+
+
+/*All anti-aliasing filters in the following conversion functions are based on
+   one of two window functions:
+  The 6-tap Lanczos window (for down-sampling and shifts):
+   sinc(\pi*t)*sinc(\pi*t/3), |t|<3  (sinc(t)==sin(t)/t)
+   0,                         |t|>=3
+  The 4-tap Mitchell window (for up-sampling):
+   7|t|^3-12|t|^2+16/3,             |t|<1
+   -(7/3)|x|^3+12|x|^2-20|x|+32/3,  |t|<2
+   0,                               |t|>=2
+  The number of taps is intentionally kept small to reduce computational
+   overhead and limit ringing.
+
+  The taps from these filters are scaled so that their sum is 1, and the result
+   is scaled by 128 and rounded to integers to create a filter whose
+   intermediate values fit inside 16 bits.
+  Coefficients are rounded in such a way as to ensure their sum is still 128,
+   which is usually equivalent to normal rounding.
+
+  Conversions which require both horizontal and vertical filtering could
+   have these steps pipelined, for less memory consumption and better cache
+   performance, but we do them separately for simplicity.*/
+
+#define OC_MINI(_a,_b)      ((_a)>(_b)?(_b):(_a))
+#define OC_MAXI(_a,_b)      ((_a)<(_b)?(_b):(_a))
+#define OC_CLAMPI(_a,_b,_c) (OC_MAXI(_a,OC_MINI(_b,_c)))
+
+/*420jpeg chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  420mpeg2 chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  BR      |       BR      |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  BR      |       BR      |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  We use a resampling filter to shift the site locations one quarter pixel (at
+   the chroma plane's resolution) to the right.
+  The 4:2:2 modes look exactly the same, except there are twice as many chroma
+   lines, and they are vertically co-sited with the luma samples in both the
+   mpeg2 and jpeg cases (thus requiring no vertical resampling).*/
+static void y4m_42xmpeg2_42xjpeg_helper(unsigned char *_dst,
+ const unsigned char *_src,int _c_w,int _c_h){
+  int pli;
+  int y;
+  int x;
+  for(y=0;y<_c_h;y++){
+    /*Filter: [4 -17 114 35 -9 1]/128, derived from a 6-tap Lanczos
+       window.*/
+    for(x=0;x<OC_MINI(_c_w,2);x++){
+      _dst[x]=(unsigned char)OC_CLAMPI(0,(4*_src[0]-17*_src[OC_MAXI(x-1,0)]+
+       114*_src[x]+35*_src[OC_MINI(x+1,_c_w-1)]-9*_src[OC_MINI(x+2,_c_w-1)]+
+       _src[OC_MINI(x+3,_c_w-1)]+64)>>7,255);
+    }
+    for(;x<_c_w-3;x++){
+      _dst[x]=(unsigned char)OC_CLAMPI(0,(4*_src[x-2]-17*_src[x-1]+
+       114*_src[x]+35*_src[x+1]-9*_src[x+2]+_src[x+3]+64)>>7,255);
+    }
+    for(;x<_c_w;x++){
+      _dst[x]=(unsigned char)OC_CLAMPI(0,(4*_src[x-2]-17*_src[x-1]+
+       114*_src[x]+35*_src[OC_MINI(x+1,_c_w-1)]-9*_src[OC_MINI(x+2,_c_w-1)]+
+       _src[_c_w-1]+64)>>7,255);
+    }
+    _dst+=_c_w;
+    _src+=_c_w;
+  }
+}
+
+/*Handles both 422 and 420mpeg2 to 422jpeg and 420jpeg, respectively.*/
+static void y4m_convert_42xmpeg2_42xjpeg(y4m_input *_y4m,unsigned char *_dst,
+ unsigned char *_aux){
+  int c_w;
+  int c_h;
+  int c_sz;
+  int pli;
+  int y;
+  int x;
+  /*Skip past the luma data.*/
+  _dst+=_y4m->pic_w*_y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w=(_y4m->pic_w+_y4m->dst_c_dec_h-1)/_y4m->dst_c_dec_h;
+  c_h=(_y4m->pic_h+_y4m->dst_c_dec_v-1)/_y4m->dst_c_dec_v;
+  c_sz=c_w*c_h;
+  for(pli=1;pli<3;pli++){
+    y4m_42xmpeg2_42xjpeg_helper(_dst,_aux,c_w,c_h);
+    _dst+=c_sz;
+    _aux+=c_sz;
+  }
+}
+
+/*This format is only used for interlaced content, but is included for
+   completeness.
+
+  420jpeg chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  420paldv chroma samples are sited like:
+  YR------Y-------YR------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YB------Y-------YB------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YR------Y-------YR------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YB------Y-------YB------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  We use a resampling filter to shift the site locations one quarter pixel (at
+   the chroma plane's resolution) to the right.
+  Then we use another filter to move the C_r location down one quarter pixel,
+   and the C_b location up one quarter pixel.*/
+static void y4m_convert_42xpaldv_42xjpeg(y4m_input *_y4m,unsigned char *_dst,
+ unsigned char *_aux){
+  unsigned char *tmp;
+  int            c_w;
+  int            c_h;
+  int            c_sz;
+  int            pli;
+  int            y;
+  int            x;
+  /*Skip past the luma data.*/
+  _dst+=_y4m->pic_w*_y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w=(_y4m->pic_w+1)/2;
+  c_h=(_y4m->pic_h+_y4m->dst_c_dec_h-1)/_y4m->dst_c_dec_h;
+  c_sz=c_w*c_h;
+  tmp=_aux+2*c_sz;
+  for(pli=1;pli<3;pli++){
+    /*First do the horizontal re-sampling.
+      This is the same as the mpeg2 case, except that after the horizontal
+       case, we need to apply a second vertical filter.*/
+    y4m_42xmpeg2_42xjpeg_helper(tmp,_aux,c_w,c_h);
+    _aux+=c_sz;
+    switch(pli){
+      case 1:{
+        /*Slide C_b up a quarter-pel.
+          This is the same filter used above, but in the other order.*/
+        for(x=0;x<c_w;x++){
+          for(y=0;y<OC_MINI(c_h,3);y++){
+            _dst[y*c_w]=(unsigned char)OC_CLAMPI(0,(tmp[0]
+             -9*tmp[OC_MAXI(y-2,0)*c_w]+35*tmp[OC_MAXI(y-1,0)*c_w]
+             +114*tmp[y*c_w]-17*tmp[OC_MINI(y+1,c_h-1)*c_w]
+             +4*tmp[OC_MINI(y+2,c_h-1)*c_w]+64)>>7,255);
+          }
+          for(;y<c_h-2;y++){
+            _dst[y*c_w]=(unsigned char)OC_CLAMPI(0,(tmp[(y-3)*c_w]
+             -9*tmp[(y-2)*c_w]+35*tmp[(y-1)*c_w]+114*tmp[y*c_w]
+             -17*tmp[(y+1)*c_w]+4*tmp[(y+2)*c_w]+64)>>7,255);
+          }
+          for(;y<c_h;y++){
+            _dst[y*c_w]=(unsigned char)OC_CLAMPI(0,(tmp[(y-3)*c_w]
+             -9*tmp[(y-2)*c_w]+35*tmp[(y-1)*c_w]+114*tmp[y*c_w]
+             -17*tmp[OC_MINI(y+1,c_h-1)*c_w]+4*tmp[(c_h-1)*c_w]+64)>>7,255);
+          }
+          _dst++;
+          tmp++;
+        }
+        _dst+=c_sz-c_w;
+        tmp-=c_w;
+      }break;
+      case 2:{
+        /*Slide C_r down a quarter-pel.
+          This is the same as the horizontal filter.*/
+        for(x=0;x<c_w;x++){
+          for(y=0;y<OC_MINI(c_h,2);y++){
+            _dst[y*c_w]=(unsigned char)OC_CLAMPI(0,(4*tmp[0]
+             -17*tmp[OC_MAXI(y-1,0)*c_w]+114*tmp[y*c_w]
+             +35*tmp[OC_MINI(y+1,c_h-1)*c_w]-9*tmp[OC_MINI(y+2,c_h-1)*c_w]
+             +tmp[OC_MINI(y+3,c_h-1)*c_w]+64)>>7,255);
+          }
+          for(;y<c_h-3;y++){
+            _dst[y*c_w]=(unsigned char)OC_CLAMPI(0,(4*tmp[(y-2)*c_w]
+             -17*tmp[(y-1)*c_w]+114*tmp[y*c_w]+35*tmp[(y+1)*c_w]
+             -9*tmp[(y+2)*c_w]+tmp[(y+3)*c_w]+64)>>7,255);
+          }
+          for(;y<c_h;y++){
+            _dst[y*c_w]=(unsigned char)OC_CLAMPI(0,(4*tmp[(y-2)*c_w]
+             -17*tmp[(y-1)*c_w]+114*tmp[y*c_w]+35*tmp[OC_MINI(y+1,c_h-1)*c_w]
+             -9*tmp[OC_MINI(y+2,c_h-1)*c_w]+tmp[(c_h-1)*c_w]+64)>>7,255);
+          }
+          _dst++;
+          tmp++;
+        }
+      }break;
+    }
+    /*For actual interlaced material, this would have to be done separately on
+       each field, and the shift amounts would be different.
+      C_r moves down 1/8, C_b up 3/8 in the top field, and C_r moves down 3/8,
+       C_b up 1/8 in the bottom field.
+      The corresponding filters would be:
+       Down 1/8 (reverse order for up): [3 -11 125 15 -4 0]/128
+       Down 3/8 (reverse order for up): [4 -19 98 56 -13 2]/128*/
+  }
+}
+
+/*Perform vertical filtering to reduce a single plane from 4:2:2 to 4:2:0.
+  This is used as a helper by several converation routines.*/
+static void y4m_422jpeg_420jpeg_helper(unsigned char *_dst,
+ const unsigned char *_src,int _c_w,int _c_h){
+  int y;
+  int x;
+  /*Filter: [3 -17 78 78 -17 3]/128, derived from a 6-tap Lanczos window.*/
+  for(x=0;x<_c_w;x++){
+    for(y=0;y<OC_MINI(_c_h,2);y+=2){
+      _dst[(y>>1)*_c_w]=OC_CLAMPI(0,(64*_src[0]
+       +78*_src[OC_MINI(1,_c_h-1)*_c_w]
+       -17*_src[OC_MINI(2,_c_h-1)*_c_w]
+       +3*_src[OC_MINI(3,_c_h-1)*_c_w]+64)>>7,255);
+    }
+    for(;y<_c_h-3;y+=2){
+      _dst[(y>>1)*_c_w]=OC_CLAMPI(0,(3*(_src[(y-2)*_c_w]+_src[(y+3)*_c_w])
+       -17*(_src[(y-1)*_c_w]+_src[(y+2)*_c_w])
+       +78*(_src[y*_c_w]+_src[(y+1)*_c_w])+64)>>7,255);
+    }
+    for(;y<_c_h;y+=2){
+      _dst[(y>>1)*_c_w]=OC_CLAMPI(0,(3*(_src[(y-2)*_c_w]
+       +_src[(_c_h-1)*_c_w])-17*(_src[(y-1)*_c_w]
+       +_src[OC_MINI(y+2,_c_h-1)*_c_w])
+       +78*(_src[y*_c_w]+_src[OC_MINI(y+1,_c_h-1)*_c_w])+64)>>7,255);
+    }
+    _src++;
+    _dst++;
+  }
+}
+
+/*420jpeg chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  422jpeg chroma samples are sited like:
+  Y---BR--Y-------Y---BR--Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y---BR--Y-------Y---BR--Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y---BR--Y-------Y---BR--Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y---BR--Y-------Y---BR--Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  We use a resampling filter to decimate the chroma planes by two in the
+   vertical direction.*/
+static void y4m_convert_422jpeg_420jpeg(y4m_input *_y4m,unsigned char *_dst,
+ unsigned char *_aux){
+  int c_w;
+  int c_h;
+  int c_sz;
+  int dst_c_w;
+  int dst_c_h;
+  int dst_c_sz;
+  int tmp_sz;
+  int pic_sz;
+  int pli;
+  /*Skip past the luma data.*/
+  _dst+=_y4m->pic_w*_y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w=(_y4m->pic_w+_y4m->src_c_dec_h-1)/_y4m->src_c_dec_h;
+  c_h=_y4m->pic_h;
+  dst_c_w=(_y4m->pic_w+_y4m->dst_c_dec_h-1)/_y4m->dst_c_dec_h;
+  dst_c_h=(_y4m->pic_h+_y4m->dst_c_dec_v-1)/_y4m->dst_c_dec_v;
+  c_sz=c_w*c_h;
+  dst_c_sz=dst_c_w*dst_c_h;
+  for(pli=1;pli<3;pli++){
+    y4m_422jpeg_420jpeg_helper(_dst,_aux,c_w,c_h);
+    _aux+=c_sz;
+    _dst+=dst_c_sz;
+  }
+}
+
+/*420jpeg chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  422 chroma samples are sited like:
+  YBR-----Y-------YBR-----Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------YBR-----Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------YBR-----Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------YBR-----Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  We use a resampling filter to shift the original site locations one quarter
+   pixel (at the original chroma resolution) to the right.
+  Then we use a second resampling filter to decimate the chroma planes by two
+   in the vertical direction.*/
+static void y4m_convert_422_420jpeg(y4m_input *_y4m,unsigned char *_dst,
+ unsigned char *_aux){
+  unsigned char *tmp;
+  int            c_w;
+  int            c_h;
+  int            c_sz;
+  int            dst_c_w;
+  int            dst_c_h;
+  int            dst_c_sz;
+  int            pli;
+  int            y;
+  int            x;
+  /*Skip past the luma data.*/
+  _dst+=_y4m->pic_w*_y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w=(_y4m->pic_w+_y4m->src_c_dec_h-1)/_y4m->src_c_dec_h;
+  c_h=_y4m->pic_h;
+  dst_c_h=(_y4m->pic_h+_y4m->dst_c_dec_v-1)/_y4m->dst_c_dec_v;
+  c_sz=c_w*c_h;
+  dst_c_sz=c_w*dst_c_h;
+  tmp=_aux+2*c_sz;
+  for(pli=1;pli<3;pli++){
+    /*In reality, the horizontal and vertical steps could be pipelined, for
+       less memory consumption and better cache performance, but we do them
+       separately for simplicity.*/
+    /*First do horizontal filtering (convert to 422jpeg)*/
+    y4m_42xmpeg2_42xjpeg_helper(tmp,_aux,c_w,c_h);
+    /*Now do the vertical filtering.*/
+    y4m_422jpeg_420jpeg_helper(_dst,tmp,c_w,c_h);
+    _aux+=c_sz;
+    _dst+=dst_c_sz;
+  }
+}
+
+/*420jpeg chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  411 chroma samples are sited like:
+  YBR-----Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  We use a filter to resample at site locations one eighth pixel (at the source
+   chroma plane's horizontal resolution) and five eighths of a pixel to the
+   right.
+  Then we use another filter to decimate the planes by 2 in the vertical
+   direction.*/
+static void y4m_convert_411_420jpeg(y4m_input *_y4m,unsigned char *_dst,
+ unsigned char *_aux){
+  unsigned char *tmp;
+  int            c_w;
+  int            c_h;
+  int            c_sz;
+  int            dst_c_w;
+  int            dst_c_h;
+  int            dst_c_sz;
+  int            tmp_sz;
+  int            pli;
+  int            y;
+  int            x;
+  /*Skip past the luma data.*/
+  _dst+=_y4m->pic_w*_y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w=(_y4m->pic_w+_y4m->src_c_dec_h-1)/_y4m->src_c_dec_h;
+  c_h=_y4m->pic_h;
+  dst_c_w=(_y4m->pic_w+_y4m->dst_c_dec_h-1)/_y4m->dst_c_dec_h;
+  dst_c_h=(_y4m->pic_h+_y4m->dst_c_dec_v-1)/_y4m->dst_c_dec_v;
+  c_sz=c_w*c_h;
+  dst_c_sz=dst_c_w*dst_c_h;
+  tmp_sz=dst_c_w*c_h;
+  tmp=_aux+2*c_sz;
+  for(pli=1;pli<3;pli++){
+    /*In reality, the horizontal and vertical steps could be pipelined, for
+       less memory consumption and better cache performance, but we do them
+       separately for simplicity.*/
+    /*First do horizontal filtering (convert to 422jpeg)*/
+    for(y=0;y<c_h;y++){
+      /*Filters: [1 110 18 -1]/128 and [-3 50 86 -5]/128, both derived from a
+         4-tap Mitchell window.*/
+      for(x=0;x<OC_MINI(c_w,1);x++){
+        tmp[x<<1]=(unsigned char)OC_CLAMPI(0,(111*_aux[0]
+         +18*_aux[OC_MINI(1,c_w-1)]-_aux[OC_MINI(2,c_w-1)]+64)>>7,255);
+        tmp[x<<1|1]=(unsigned char)OC_CLAMPI(0,(47*_aux[0]
+         +86*_aux[OC_MINI(1,c_w-1)]-5*_aux[OC_MINI(2,c_w-1)]+64)>>7,255);
+      }
+      for(;x<c_w-2;x++){
+        tmp[x<<1]=(unsigned char)OC_CLAMPI(0,(_aux[x-1]+110*_aux[x]
+         +18*_aux[x+1]-_aux[x+2]+64)>>7,255);
+        tmp[x<<1|1]=(unsigned char)OC_CLAMPI(0,(-3*_aux[x-1]+50*_aux[x]
+         +86*_aux[x+1]-5*_aux[x+2]+64)>>7,255);
+      }
+      for(;x<c_w;x++){
+        tmp[x<<1]=(unsigned char)OC_CLAMPI(0,(_aux[x-1]+110*_aux[x]
+         +18*_aux[OC_MINI(x+1,c_w-1)]-_aux[c_w-1]+64)>>7,255);
+        if((x<<1|1)<dst_c_w){
+          tmp[x<<1|1]=(unsigned char)OC_CLAMPI(0,(-3*_aux[x-1]+50*_aux[x]
+           +86*_aux[OC_MINI(x+1,c_w-1)]-5*_aux[c_w-1]+64)>>7,255);
+        }
+      }
+      tmp+=dst_c_w;
+      _aux+=c_w;
+    }
+    tmp-=tmp_sz;
+    /*Now do the vertical filtering.*/
+    y4m_422jpeg_420jpeg_helper(_dst,tmp,dst_c_w,c_h);
+    _dst+=dst_c_sz;
+  }
+}
+
+/*Convert 444 to 420jpeg.*/
+static void y4m_convert_444_420jpeg(y4m_input *_y4m,unsigned char *_dst,
+ unsigned char *_aux){
+  unsigned char *tmp;
+  int            c_w;
+  int            c_h;
+  int            c_sz;
+  int            dst_c_w;
+  int            dst_c_h;
+  int            dst_c_sz;
+  int            tmp_sz;
+  int            pli;
+  int            y;
+  int            x;
+  /*Skip past the luma data.*/
+  _dst+=_y4m->pic_w*_y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w=(_y4m->pic_w+_y4m->src_c_dec_h-1)/_y4m->src_c_dec_h;
+  c_h=_y4m->pic_h;
+  dst_c_w=(_y4m->pic_w+_y4m->dst_c_dec_h-1)/_y4m->dst_c_dec_h;
+  dst_c_h=(_y4m->pic_h+_y4m->dst_c_dec_v-1)/_y4m->dst_c_dec_v;
+  c_sz=c_w*c_h;
+  dst_c_sz=dst_c_w*dst_c_h;
+  tmp_sz=dst_c_w*c_h;
+  tmp=_aux+2*c_sz;
+  for(pli=1;pli<3;pli++){
+    /*Filter: [3 -17 78 78 -17 3]/128, derived from a 6-tap Lanczos window.*/
+    for(y=0;y<c_h;y++){
+      for(x=0;x<OC_MINI(c_w,2);x+=2){
+        tmp[x>>1]=OC_CLAMPI(0,(64*_aux[0]+78*_aux[OC_MINI(1,c_w-1)]
+         -17*_aux[OC_MINI(2,c_w-1)]
+         +3*_aux[OC_MINI(3,c_w-1)]+64)>>7,255);
+      }
+      for(;x<c_w-3;x+=2){
+        tmp[x>>1]=OC_CLAMPI(0,(3*(_aux[x-2]+_aux[x+3])
+         -17*(_aux[x-1]+_aux[x+2])+78*(_aux[x]+_aux[x+1])+64)>>7,255);
+      }
+      for(;x<c_w;x+=2){
+        tmp[x>>1]=OC_CLAMPI(0,(3*(_aux[x-2]+_aux[c_w-1])-
+         17*(_aux[x-1]+_aux[OC_MINI(x+2,c_w-1)])+
+         78*(_aux[x]+_aux[OC_MINI(x+1,c_w-1)])+64)>>7,255);
+      }
+      tmp+=dst_c_w;
+      _aux+=c_w;
+    }
+    tmp-=tmp_sz;
+    /*Now do the vertical filtering.*/
+    y4m_422jpeg_420jpeg_helper(_dst,tmp,dst_c_w,c_h);
+    _dst+=dst_c_sz;
+  }
+}
+
+/*The image is padded with empty chroma components at 4:2:0.*/
+static void y4m_convert_mono_420jpeg(y4m_input *_y4m,unsigned char *_dst,
+ unsigned char *_aux){
+  int c_sz;
+  _dst+=_y4m->pic_w*_y4m->pic_h;
+  c_sz=((_y4m->pic_w+_y4m->dst_c_dec_h-1)/_y4m->dst_c_dec_h)*
+   ((_y4m->pic_h+_y4m->dst_c_dec_v-1)/_y4m->dst_c_dec_v);
+  memset(_dst,128,c_sz*2);
+}
+
+/*No conversion function needed.*/
+static void y4m_convert_null(y4m_input *_y4m,unsigned char *_dst,
+ unsigned char *_aux){
+}
+
+int y4m_input_open(y4m_input *_y4m,FILE *_fin,char *_skip,int _nskip){
+  char buffer[80];
+  int  ret;
+  int  i;
+  /*Read until newline, or 80 cols, whichever happens first.*/
+  for(i=0;i<79;i++){
+    if(_nskip>0){
+      buffer[i]=*_skip++;
+      _nskip--;
+    }
+    else{
+      ret=fread(buffer+i,1,1,_fin);
+      if(ret<1)return -1;
+    }
+    if(buffer[i]=='\n')break;
+  }
+  /*We skipped too much header data.*/
+  if(_nskip>0)return -1;
+  if(i==79){
+    fprintf(stderr,"Error parsing header; not a YUV2MPEG2 file?\n");
+    return -1;
+  }
+  buffer[i]='\0';
+  if(memcmp(buffer,"YUV4MPEG",8)){
+    fprintf(stderr,"Incomplete magic for YUV4MPEG file.\n");
+    return -1;
+  }
+  if(buffer[8]!='2'){
+    fprintf(stderr,"Incorrect YUV input file version; YUV4MPEG2 required.\n");
+  }
+  ret=y4m_parse_tags(_y4m,buffer+5);
+  if(ret<0){
+    fprintf(stderr,"Error parsing YUV4MPEG2 header.\n");
+    return ret;
+  }
+  if(_y4m->interlace=='?'){
+    fprintf(stderr,"Warning: Input video interlacing format unknown; "
+     "assuming progressive scan.\n");
+  }
+  else if(_y4m->interlace!='p'){
+    fprintf(stderr,"Input video is interlaced; "
+     "Only progressive scan handled.\n");
+    return -1;
+  }
+  if(strcmp(_y4m->chroma_type,"420")==0||
+   strcmp(_y4m->chroma_type,"420jpeg")==0){
+    _y4m->src_c_dec_h=_y4m->dst_c_dec_h=_y4m->src_c_dec_v=_y4m->dst_c_dec_v=2;
+    _y4m->dst_buf_read_sz=_y4m->pic_w*_y4m->pic_h
+     +2*((_y4m->pic_w+1)/2)*((_y4m->pic_h+1)/2);
+    /*Natively supported: no conversion required.*/
+    _y4m->aux_buf_sz=_y4m->aux_buf_read_sz=0;
+    _y4m->convert=y4m_convert_null;
+  }
+  else if(strcmp(_y4m->chroma_type,"420mpeg2")==0){
+    _y4m->src_c_dec_h=_y4m->dst_c_dec_h=_y4m->src_c_dec_v=_y4m->dst_c_dec_v=2;
+    _y4m->dst_buf_read_sz=_y4m->pic_w*_y4m->pic_h;
+    /*Chroma filter required: read into the aux buf first.*/
+    _y4m->aux_buf_sz=_y4m->aux_buf_read_sz=
+     2*((_y4m->pic_w+1)/2)*((_y4m->pic_h+1)/2);
+    _y4m->convert=y4m_convert_42xmpeg2_42xjpeg;
+  }
+  else if(strcmp(_y4m->chroma_type,"420paldv")==0){
+    _y4m->src_c_dec_h=_y4m->dst_c_dec_h=_y4m->src_c_dec_v=_y4m->dst_c_dec_v=2;
+    _y4m->dst_buf_read_sz=_y4m->pic_w*_y4m->pic_h;
+    /*Chroma filter required: read into the aux buf first.
+      We need to make two filter passes, so we need some extra space in the
+       aux buffer.*/
+    _y4m->aux_buf_sz=3*((_y4m->pic_w+1)/2)*((_y4m->pic_h+1)/2);
+    _y4m->aux_buf_read_sz=2*((_y4m->pic_w+1)/2)*((_y4m->pic_h+1)/2);
+    _y4m->convert=y4m_convert_42xpaldv_42xjpeg;
+  }
+  else if(strcmp(_y4m->chroma_type,"422jpeg")==0){
+    _y4m->src_c_dec_h=_y4m->dst_c_dec_h=2;
+    _y4m->src_c_dec_v=1;
+    _y4m->dst_c_dec_v=2;
+    _y4m->dst_buf_read_sz=_y4m->pic_w*_y4m->pic_h;
+    /*Chroma filter required: read into the aux buf first.*/
+    _y4m->aux_buf_sz=_y4m->aux_buf_read_sz=2*((_y4m->pic_w+1)/2)*_y4m->pic_h;
+    _y4m->convert=y4m_convert_422jpeg_420jpeg;
+  }
+  else if(strcmp(_y4m->chroma_type,"422")==0){
+    _y4m->src_c_dec_h=_y4m->dst_c_dec_h=2;
+    _y4m->src_c_dec_v=1;
+    _y4m->dst_c_dec_v=2;
+    _y4m->dst_buf_read_sz=_y4m->pic_w*_y4m->pic_h;
+    /*Chroma filter required: read into the aux buf first.
+      We need to make two filter passes, so we need some extra space in the
+       aux buffer.*/
+    _y4m->aux_buf_read_sz=2*((_y4m->pic_w+1)/2)*_y4m->pic_h;
+    _y4m->aux_buf_sz=_y4m->aux_buf_read_sz+((_y4m->pic_w+1)/2)*_y4m->pic_h;
+    _y4m->convert=y4m_convert_422_420jpeg;
+  }
+  else if(strcmp(_y4m->chroma_type,"411")==0){
+    _y4m->src_c_dec_h=4;
+    _y4m->dst_c_dec_h=2;
+    _y4m->src_c_dec_v=1;
+    _y4m->dst_c_dec_v=2;
+    _y4m->dst_buf_read_sz=_y4m->pic_w*_y4m->pic_h;
+    /*Chroma filter required: read into the aux buf first.
+      We need to make two filter passes, so we need some extra space in the
+       aux buffer.*/
+    _y4m->aux_buf_read_sz=2*((_y4m->pic_w+3)/4)*_y4m->pic_h;
+    _y4m->aux_buf_sz=_y4m->aux_buf_read_sz+((_y4m->pic_w+1)/2)*_y4m->pic_h;
+    _y4m->convert=y4m_convert_411_420jpeg;
+  }
+  else if(strcmp(_y4m->chroma_type,"444")==0){
+    _y4m->src_c_dec_h=1;
+    _y4m->dst_c_dec_h=2;
+    _y4m->src_c_dec_v=1;
+    _y4m->dst_c_dec_v=2;
+    _y4m->dst_buf_read_sz=_y4m->pic_w*_y4m->pic_h;
+    /*Chroma filter required: read into the aux buf first.
+      We need to make two filter passes, so we need some extra space in the
+       aux buffer.*/
+    _y4m->aux_buf_read_sz=2*_y4m->pic_w*_y4m->pic_h;
+    _y4m->aux_buf_sz=_y4m->aux_buf_read_sz+((_y4m->pic_w+1)/2)*_y4m->pic_h;
+    _y4m->convert=y4m_convert_444_420jpeg;
+  }
+  else if(strcmp(_y4m->chroma_type,"444alpha")==0){
+    _y4m->src_c_dec_h=1;
+    _y4m->dst_c_dec_h=2;
+    _y4m->src_c_dec_v=1;
+    _y4m->dst_c_dec_v=2;
+    _y4m->dst_buf_read_sz=_y4m->pic_w*_y4m->pic_h;
+    /*Chroma filter required: read into the aux buf first.
+      We need to make two filter passes, so we need some extra space in the
+       aux buffer.
+      The extra plane also gets read into the aux buf.
+      It will be discarded.*/
+    _y4m->aux_buf_sz=_y4m->aux_buf_read_sz=3*_y4m->pic_w*_y4m->pic_h;
+    _y4m->convert=y4m_convert_444_420jpeg;
+  }
+  else if(strcmp(_y4m->chroma_type,"mono")==0){
+    _y4m->src_c_dec_h=_y4m->src_c_dec_v=0;
+    _y4m->dst_c_dec_h=_y4m->dst_c_dec_v=2;
+    _y4m->dst_buf_read_sz=_y4m->pic_w*_y4m->pic_h;
+    /*No extra space required, but we need to clear the chroma planes.*/
+    _y4m->aux_buf_sz=_y4m->aux_buf_read_sz=0;
+    _y4m->convert=y4m_convert_mono_420jpeg;
+  }
+  else{
+    fprintf(stderr,"Unknown chroma sampling type: %s\n",_y4m->chroma_type);
+    return -1;
+  }
+  /*The size of the final frame buffers is always computed from the
+     destination chroma decimation type.*/
+  _y4m->dst_buf_sz=_y4m->pic_w*_y4m->pic_h
+   +2*((_y4m->pic_w+_y4m->dst_c_dec_h-1)/_y4m->dst_c_dec_h)*
+   ((_y4m->pic_h+_y4m->dst_c_dec_v-1)/_y4m->dst_c_dec_v);
+  _y4m->dst_buf=(unsigned char *)malloc(_y4m->dst_buf_sz);
+  _y4m->aux_buf=(unsigned char *)malloc(_y4m->aux_buf_sz);
+  return 0;
+}
+
+void y4m_input_close(y4m_input *_y4m){
+  free(_y4m->dst_buf);
+  free(_y4m->aux_buf);
+}
+
+int y4m_input_fetch_frame(y4m_input *_y4m,FILE *_fin,vpx_image_t *_img){
+  char frame[6];
+  int  pic_sz;
+  int  frame_c_w;
+  int  frame_c_h;
+  int  c_w;
+  int  c_h;
+  int  c_sz;
+  int  ret;
+  /*Read and skip the frame header.*/
+  ret=fread(frame,1,6,_fin);
+  if(ret<6)return 0;
+  if(memcmp(frame,"FRAME",5)){
+    fprintf(stderr,"Loss of framing in Y4M input data\n");
+    return -1;
+  }
+  if(frame[5]!='\n'){
+    char c;
+    int  j;
+    for(j=0;j<79&&fread(&c,1,1,_fin)&&c!='\n';j++);
+    if(j==79){
+      fprintf(stderr,"Error parsing Y4M frame header\n");
+      return -1;
+    }
+  }
+  /*Read the frame data that needs no conversion.*/
+  if(fread(_y4m->dst_buf,1,_y4m->dst_buf_read_sz,_fin)!=_y4m->dst_buf_read_sz){
+    fprintf(stderr,"Error reading Y4M frame data.\n");
+    return -1;
+  }
+  /*Read the frame data that does need conversion.*/
+  if(fread(_y4m->aux_buf,1,_y4m->aux_buf_read_sz,_fin)!=_y4m->aux_buf_read_sz){
+    fprintf(stderr,"Error reading Y4M frame data.\n");
+    return -1;
+  }
+  /*Now convert the just read frame.*/
+  (*_y4m->convert)(_y4m,_y4m->dst_buf,_y4m->aux_buf);
+  /*Fill in the frame buffer pointers.
+    We don't use vpx_img_wrap() because it forces padding for odd picture
+     sizes, which would require a separate fread call for every row.*/
+  memset(_img,0,sizeof(*_img));
+  /*Y4M has the planes in Y'CbCr order, which libvpx calls Y, U, and V.*/
+  _img->fmt=IMG_FMT_I420;
+  _img->w=_img->d_w=_y4m->pic_w;
+  _img->h=_img->d_h=_y4m->pic_h;
+  /*This is hard-coded to 4:2:0 for now, as that's all VP8 supports.*/
+  _img->x_chroma_shift=1;
+  _img->y_chroma_shift=1;
+  _img->bps=12;
+  /*Set up the buffer pointers.*/
+  pic_sz=_y4m->pic_w*_y4m->pic_h;
+  c_w=(_y4m->pic_w+_y4m->dst_c_dec_h-1)/_y4m->dst_c_dec_h;
+  c_h=(_y4m->pic_h+_y4m->dst_c_dec_v-1)/_y4m->dst_c_dec_v;
+  c_sz=c_w*c_h;
+  _img->stride[PLANE_Y]=_y4m->pic_w;
+  _img->stride[PLANE_U]=_img->stride[PLANE_V]=c_w;
+  _img->planes[PLANE_Y]=_y4m->dst_buf;
+  _img->planes[PLANE_U]=_y4m->dst_buf+pic_sz;
+  _img->planes[PLANE_V]=_y4m->dst_buf+pic_sz+c_sz;
+  return 0;
+}
diff --git a/y4minput.h b/y4minput.h
new file mode 100644 (file)
index 0000000..1534875
--- /dev/null
@@ -0,0 +1,59 @@
+/*
+ *  Copyright (c) 2010 The VP8 project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license and patent
+ *  grant that can be found in the LICENSE file in the root of the source
+ *  tree. All contributing project authors may be found in the AUTHORS
+ *  file in the root of the source tree.
+ *
+ *  Based on code from the OggTheora software codec source code,
+ *  Copyright (C) 2002-2010 The Xiph.Org Foundation and contributors.
+ */
+#if !defined(_y4minput_H)
+# define _y4minput_H (1)
+# include <stdio.h>
+# include "vpx/vpx_image.h"
+
+
+
+typedef struct y4m_input y4m_input;
+
+
+
+/*The function used to perform chroma conversion.*/
+typedef void (*y4m_convert_func)(y4m_input *_y4m,
+ unsigned char *_dst,unsigned char *_src);
+
+
+
+struct y4m_input{
+  int               pic_w;
+  int               pic_h;
+  int               fps_n;
+  int               fps_d;
+  int               par_n;
+  int               par_d;
+  char              interlace;
+  int               src_c_dec_h;
+  int               src_c_dec_v;
+  int               dst_c_dec_h;
+  int               dst_c_dec_v;
+  char              chroma_type[16];
+  /*The size of each converted frame buffer.*/
+  size_t            dst_buf_sz;
+  /*The amount to read directly into the converted frame buffer.*/
+  size_t            dst_buf_read_sz;
+  /*The size of the auxilliary buffer.*/
+  size_t            aux_buf_sz;
+  /*The amount to read into the auxilliary buffer.*/
+  size_t            aux_buf_read_sz;
+  y4m_convert_func  convert;
+  unsigned char    *dst_buf;
+  unsigned char    *aux_buf;
+};
+
+int y4m_input_open(y4m_input *_y4m,FILE *_fin,char *_skip,int _nskip);
+void y4m_input_close(y4m_input *_y4m);
+int y4m_input_fetch_frame(y4m_input *_y4m,FILE *_fin,vpx_image_t *img);
+
+#endif