3 * Copyright (c) 2015 Donny Yang
5 * first version by Donny Yang <work@kota.moe>
7 * This file is part of FFmpeg.
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
25 #include "libavutil/avassert.h"
26 #include "libavutil/crc.h"
27 #include "libavutil/intreadwrite.h"
28 #include "libavutil/log.h"
29 #include "libavutil/opt.h"
30 #include "libavcodec/apng.h"
31 #include "libavcodec/png.h"
33 typedef struct APNGMuxContext {
37 AVRational last_delay;
40 uint32_t frame_number;
42 AVPacket *prev_packet;
43 AVRational prev_delay;
51 static const uint8_t *apng_find_chunk(uint32_t tag, const uint8_t *buf,
55 for (b = 0; AV_RB32(buf + b) + 12ULL <= length - b; b += AV_RB32(buf + b) + 12ULL)
56 if (AV_RB32(&buf[b + 4]) == tag)
61 static void apng_write_chunk(AVIOContext *io_context, uint32_t tag,
62 uint8_t *buf, size_t length)
64 const AVCRC *crc_table = av_crc_get_table(AV_CRC_32_IEEE_LE);
68 av_assert0(crc_table);
70 avio_wb32(io_context, length);
72 crc = av_crc(crc_table, crc, tagbuf, 4);
73 avio_wb32(io_context, tag);
75 crc = av_crc(crc_table, crc, buf, length);
76 avio_write(io_context, buf, length);
78 avio_wb32(io_context, ~crc);
81 static int apng_write_header(AVFormatContext *format_context)
83 APNGMuxContext *apng = format_context->priv_data;
84 AVCodecParameters *par = format_context->streams[0]->codecpar;
86 if (format_context->nb_streams != 1 ||
87 format_context->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO ||
88 format_context->streams[0]->codecpar->codec_id != AV_CODEC_ID_APNG) {
89 av_log(format_context, AV_LOG_ERROR,
90 "APNG muxer supports only a single video APNG stream.\n");
91 return AVERROR(EINVAL);
94 if (apng->last_delay.num > UINT16_MAX || apng->last_delay.den > UINT16_MAX) {
95 av_reduce(&apng->last_delay.num, &apng->last_delay.den,
96 apng->last_delay.num, apng->last_delay.den, UINT16_MAX);
97 av_log(format_context, AV_LOG_WARNING,
98 "Last frame delay is too precise. Reducing to %d/%d (%f).\n",
99 apng->last_delay.num, apng->last_delay.den, (double)apng->last_delay.num / apng->last_delay.den);
102 avio_wb64(format_context->pb, PNGSIG);
103 // Remaining headers are written when they are copied from the encoder
105 if (par->extradata_size) {
106 apng->extra_data = av_mallocz(par->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
107 if (!apng->extra_data)
108 return AVERROR(ENOMEM);
109 apng->extra_data_size = par->extradata_size;
110 memcpy(apng->extra_data, par->extradata, par->extradata_size);
116 static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
118 APNGMuxContext *apng = format_context->priv_data;
119 AVIOContext *io_context = format_context->pb;
120 AVStream *codec_stream = format_context->streams[0];
121 uint8_t *side_data = NULL;
122 size_t side_data_size;
124 av_assert0(apng->prev_packet);
126 side_data = av_packet_get_side_data(apng->prev_packet, AV_PKT_DATA_NEW_EXTRADATA, &side_data_size);
128 if (side_data_size) {
129 av_freep(&apng->extra_data);
130 apng->extra_data = av_mallocz(side_data_size + AV_INPUT_BUFFER_PADDING_SIZE);
131 if (!apng->extra_data)
132 return AVERROR(ENOMEM);
133 apng->extra_data_size = side_data_size;
134 memcpy(apng->extra_data, side_data, apng->extra_data_size);
137 if (apng->frame_number == 0 && !packet) {
138 const uint8_t *existing_acTL_chunk;
139 const uint8_t *existing_fcTL_chunk;
141 av_log(format_context, AV_LOG_INFO, "Only a single frame so saving as a normal PNG.\n");
143 // Write normal PNG headers without acTL chunk
144 existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
145 if (existing_acTL_chunk) {
146 const uint8_t *chunk_after_acTL = existing_acTL_chunk + AV_RB32(existing_acTL_chunk) + 12;
147 avio_write(io_context, apng->extra_data, existing_acTL_chunk - apng->extra_data);
148 avio_write(io_context, chunk_after_acTL, apng->extra_data + apng->extra_data_size - chunk_after_acTL);
150 avio_write(io_context, apng->extra_data, apng->extra_data_size);
153 // Write frame data without fcTL chunk
154 existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
155 if (existing_fcTL_chunk) {
156 const uint8_t *chunk_after_fcTL = existing_fcTL_chunk + AV_RB32(existing_fcTL_chunk) + 12;
157 avio_write(io_context, apng->prev_packet->data, existing_fcTL_chunk - apng->prev_packet->data);
158 avio_write(io_context, chunk_after_fcTL, apng->prev_packet->data + apng->prev_packet->size - chunk_after_fcTL);
160 avio_write(io_context, apng->prev_packet->data, apng->prev_packet->size);
163 const uint8_t *data, *data_end;
164 const uint8_t *existing_fcTL_chunk;
166 if (apng->frame_number == 0) {
167 const uint8_t *existing_acTL_chunk;
169 // Write normal PNG headers
170 avio_write(io_context, apng->extra_data, apng->extra_data_size);
172 existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
173 if (!existing_acTL_chunk) {
175 // Write animation control header
176 apng->acTL_offset = avio_tell(io_context);
177 AV_WB32(buf, UINT_MAX); // number of frames (filled in later)
178 AV_WB32(buf + 4, apng->plays);
179 apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
183 data = apng->prev_packet->data;
184 data_end = data + apng->prev_packet->size;
185 existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
186 if (existing_fcTL_chunk) {
189 if (AV_RB32(existing_fcTL_chunk) != APNG_FCTL_CHUNK_SIZE)
190 return AVERROR_INVALIDDATA;
192 existing_fcTL_chunk += 8;
193 delay.num = AV_RB16(existing_fcTL_chunk + 20);
194 delay.den = AV_RB16(existing_fcTL_chunk + 22);
196 if (delay.num == 0 && delay.den == 0) {
197 uint8_t new_fcTL_chunk[APNG_FCTL_CHUNK_SIZE];
200 int64_t delay_num_raw = (packet->dts - apng->prev_packet->dts) * codec_stream->time_base.num;
201 int64_t delay_den_raw = codec_stream->time_base.den;
202 if (!av_reduce(&delay.num, &delay.den, delay_num_raw, delay_den_raw, UINT16_MAX) &&
203 !apng->framerate_warned) {
204 av_log(format_context, AV_LOG_WARNING,
205 "Frame rate is too high or specified too precisely. Unable to copy losslessly.\n");
206 apng->framerate_warned = 1;
208 } else if (apng->last_delay.num > 0) {
209 delay = apng->last_delay;
211 delay = apng->prev_delay;
214 avio_write(io_context, data, (existing_fcTL_chunk - 8) - data);
215 data = existing_fcTL_chunk + APNG_FCTL_CHUNK_SIZE + 4 /* CRC-32 */;
216 // Update frame control header with new delay
217 memcpy(new_fcTL_chunk, existing_fcTL_chunk, sizeof(new_fcTL_chunk));
218 AV_WB16(new_fcTL_chunk + 20, delay.num);
219 AV_WB16(new_fcTL_chunk + 22, delay.den);
220 apng_write_chunk(io_context, MKBETAG('f', 'c', 'T', 'L'),
221 new_fcTL_chunk, sizeof(new_fcTL_chunk));
223 apng->prev_delay = delay;
227 avio_write(io_context, data, data_end - data);
229 ++apng->frame_number;
231 av_packet_unref(apng->prev_packet);
233 av_packet_ref(apng->prev_packet, packet);
237 static int apng_write_packet(AVFormatContext *format_context, AVPacket *packet)
239 APNGMuxContext *apng = format_context->priv_data;
242 if (!apng->prev_packet) {
243 apng->prev_packet = av_packet_alloc();
244 if (!apng->prev_packet)
245 return AVERROR(ENOMEM);
247 av_packet_ref(apng->prev_packet, packet);
249 ret = flush_packet(format_context, packet);
257 static int apng_write_trailer(AVFormatContext *format_context)
259 APNGMuxContext *apng = format_context->priv_data;
260 AVIOContext *io_context = format_context->pb;
264 if (apng->prev_packet) {
265 ret = flush_packet(format_context, NULL);
270 apng_write_chunk(io_context, MKBETAG('I', 'E', 'N', 'D'), NULL, 0);
272 if (apng->acTL_offset && (io_context->seekable & AVIO_SEEKABLE_NORMAL)) {
273 avio_seek(io_context, apng->acTL_offset, SEEK_SET);
275 AV_WB32(buf, apng->frame_number);
276 AV_WB32(buf + 4, apng->plays);
277 apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
283 static void apng_deinit(AVFormatContext *s)
285 APNGMuxContext *apng = s->priv_data;
287 av_packet_free(&apng->prev_packet);
288 av_freep(&apng->extra_data);
289 apng->extra_data_size = 0;
292 #define OFFSET(x) offsetof(APNGMuxContext, x)
293 #define ENC AV_OPT_FLAG_ENCODING_PARAM
294 static const AVOption options[] = {
295 { "plays", "Number of times to play the output: 0 - infinite loop, 1 - no loop", OFFSET(plays),
296 AV_OPT_TYPE_INT, { .i64 = 1 }, 0, UINT16_MAX, ENC },
297 { "final_delay", "Force delay after the last frame", OFFSET(last_delay),
298 AV_OPT_TYPE_RATIONAL, { .dbl = 0 }, 0, UINT16_MAX, ENC },
302 static const AVClass apng_muxer_class = {
303 .class_name = "APNG muxer",
304 .item_name = av_default_item_name,
305 .version = LIBAVUTIL_VERSION_INT,
309 const AVOutputFormat ff_apng_muxer = {
311 .long_name = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
312 .mime_type = "image/png",
313 .extensions = "apng",
314 .priv_data_size = sizeof(APNGMuxContext),
315 .audio_codec = AV_CODEC_ID_NONE,
316 .video_codec = AV_CODEC_ID_APNG,
317 .write_header = apng_write_header,
318 .write_packet = apng_write_packet,
319 .write_trailer = apng_write_trailer,
320 .deinit = apng_deinit,
321 .priv_class = &apng_muxer_class,
322 .flags = AVFMT_VARIABLE_FPS,