From a49ff7a45171d6d03d79df26bf2dbd0a8b8ab976 Mon Sep 17 00:00:00 2001 From: Robert Swain Date: Sun, 15 Jul 2012 23:35:07 +0200 Subject: [PATCH] docs: Update interlaced video docs An interlaced buffer flag has been added and some other changes in operation needed addressing since the last update to the document. --- docs/design/part-interlaced-video.txt | 44 +++++++++++++++++++++-------------- 1 file changed, 27 insertions(+), 17 deletions(-) diff --git a/docs/design/part-interlaced-video.txt b/docs/design/part-interlaced-video.txt index efa889a..4ac678e 100644 --- a/docs/design/part-interlaced-video.txt +++ b/docs/design/part-interlaced-video.txt @@ -25,13 +25,16 @@ telecine states is that in the telecine state, buffers containing two fields may be progressive. Tools for identification: -- Caps - - interlace-mode - string - "progressive"/"interleaved"/"mixed" -- Flags - GST_VIDEO_FLAG_... +- GstVideoInfo + - GstVideoInterlaceMode - enum - GST_VIDEO_INTERLACE_MODE_... + - PROGRESSIVE + - INTERLEAVED + - MIXED +- Buffers flags - GST_VIDEO_BUFFER_FLAG_... - TFF - RFF - ONEFIELD - - PROGRESSIVE + - INTERLACED Identification of Buffer States @@ -44,41 +47,38 @@ different states nor are they necessarily required nor make sense in all cases. Progressive ........... -If the caps have no interlace-mode field on a source pad, or have -interlace-mode="progressive", then the buffer is progressive. The lack of the -interlace-mode field on a sink pad means that the element is not concerned -about the mode and can handle all. Note the possibility for progressive buffers -in telecine streams as well. +If the interlace mode in the video info corresponding to a buffer is +"progressive", then the buffer is progressive. Plain Interlaced ................ -If the caps have interlace-mode="interleaved" or "fields", then the buffer is -plain interlaced. +If the video info interlace mode is "interleaved", then the buffer is plain +interlaced. -GST_VIDEO_FLAG_TFF indicates whether the top or bottom field is to be +GST_VIDEO_BUFFER_FLAG_TFF indicates whether the top or bottom field is to be displayed first. The timestamp on the buffer corresponds to the first field. -GST_VIDEO_FLAG_RFF indicates that the first field (indicated by the TFF flag) +GST_VIDEO_BUFFER_FLAG_RFF indicates that the first field (indicated by the TFF flag) should be repeated. This is generally only used for telecine purposes but as the telecine state was added long after the interlaced state was added and defined, this flag remains valid for plain interlaced buffers. -GST_VIDEO_FLAG_ONEFIELD means that only the field indicated through the TFF +GST_VIDEO_BUFFER_FLAG_ONEFIELD means that only the field indicated through the TFF flag is to be used. The other field should be ignored. Telecine ........ -If the caps have interlace-mode=mixed then the buffers are in some form of +If video info interlace mode is "mixed" then the buffers are in some form of telecine state. The TFF and ONEFIELD flags have the same semantics as for the plain interlaced state. -GST_VIDEO_FLAG_RFF in the telecine state indicates that the buffer contains +GST_VIDEO_BUFFER_FLAG_RFF in the telecine state indicates that the buffer contains only repeated fields that are present in other buffers and are as such unneeded. For example, in a sequence of three telecined frames, we might have: @@ -87,11 +87,21 @@ AtAb AtBb BtBb In this situation, we only need the first and third buffers as the second buffer contains fields present in the first and third. +Note that the following state can have its second buffer identified using the +ONEFIELD flag (and TFF not set): + +AtAb AtBb BtCb + The telecine state requires one additional flag to be able to identify progressive buffers. -The presence of the GST_VIDEO_FLAG_INTERLACED means that the buffer is an +The presence of the GST_VIDEO_BUFFER_FLAG_INTERLACED means that the buffer is an 'interlaced' or 'mixed' buffer that contains two fields that, when combined with fields from adjacent buffers, allow reconstruction of progressive frames. The absence of the flag implies the buffer containing two fields is a progressive frame. + +For example in the following sequence, the third buffer would be mixed (yes, it +is a strange pattern, but it can happen): + +AtAb AtBb BtCb CtDb DtDb -- 2.7.4