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docs: interlaced video: Update docs

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Robert Swain 2012-01-17 18:13:43 +01:00
parent 8dcb565221
commit b3eacd7dec
1 changed files with 22 additions and 26 deletions
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48
docs/design/part-interlaced-video.txt
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@ -1,5 +1,3 @@
** outdated **
Interlaced Video Interlaced Video
================ ================
@ -22,15 +20,14 @@ Possible states:
- Three fields - this should be a progressive buffer with a repeated 'first' - Three fields - this should be a progressive buffer with a repeated 'first'
field that can be used for telecine pulldown field that can be used for telecine pulldown
Note: it can be seen that the different between the plain interlaced and Note: It can be seen that the difference between the plain interlaced and
telecine states is that in the telecine state, buffers containing two fields may telecine states is that in the telecine state, buffers containing two fields may
be progressive. be progressive.
Tools for identification: Tools for identification:
- Caps - Caps
- interlaced - boolean - interlace-mode - string - "progressive"/"interleaved"/"mixed"
- interlacing-method - string - "unknown"/"telecine" - Flags - GST_VIDEO_FLAG_...
- Flags - GST_VIDEO_BUFFER_...
- TFF - TFF
- RFF - RFF
- ONEFIELD - ONEFIELD
@ -47,42 +44,41 @@ different states nor are they necessarily required nor make sense in all cases.
Progressive Progressive
........... ...........
If the caps have no interlaced field, or have interlaced=false, then the buffer If the caps have no interlace-mode field on a source pad, or have
is progressive. Note the possibility for progressive buffers in telecine streams interlace-mode="progressive", then the buffer is progressive. The lack of the
as well. 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.
Plain Interlaced Plain Interlaced
................ ................
If the caps have interlaced=true and either do not contain the If the caps have interlace-mode="interleaved" or "fields", then the buffer is
interlacing-method field or contain interlacing-method=unknown, then the buffer plain interlaced.
is plain interlaced.
GST_VIDEO_BUFFER_TFF indicates whether the top or bottom field is to be GST_VIDEO_FLAG_TFF indicates whether the top or bottom field is to be
displayed first. The timestamp on the buffer corresponds to the first field. displayed first. The timestamp on the buffer corresponds to the first field.
(FIXME - is the duration of the buffer the duration of both fields; each field's
duration is half the buffer duration)
GST_VIDEO_BUFFER_RFF indicates that the first field (indicated by the TFF flag) GST_VIDEO_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 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, telecine state was added long after the interlaced state was added and defined,
this flag remains valid for plain interlaced buffers. this flag remains valid for plain interlaced buffers.
GST_VIDEO_BUFFER_ONEFIELD means that only the field indicated through the TFF GST_VIDEO_FLAG_ONEFIELD means that only the field indicated through the TFF
flag is to be used. The other field should be ignored. flag is to be used. The other field should be ignored.
Telecine Telecine
........ ........
If the caps have interlaced=true and interlacing-method=telecine then the If the caps have interlace-mode=mixed then the buffers are in some form of
buffers are in some form of telecine state. telecine state.
The TFF and ONEFIELD flags have the same semantics as for the plain interlaced The TFF and ONEFIELD flags have the same semantics as for the plain interlaced
state. state.
GST_VIDEO_BUFFER_RFF in the telecine state indicates that the buffer contains GST_VIDEO_FLAG_RFF in the telecine state indicates that the buffer contains
only repeated fields that are present in other buffers and are as such 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: unneeded. For example, in a sequence of three telecined frames, we might have:
@ -91,11 +87,11 @@ AtAb AtBb BtBb
In this situation, we only need the first and third buffers as the second In this situation, we only need the first and third buffers as the second
buffer contains fields present in the first and third. buffer contains fields present in the first and third.
The telecine state require one additional flag to be able to identify The telecine state requires one additional flag to be able to identify
progressive buffers. progressive buffers.
GST_VIDEO_BUFFER_PROGRESSIVE means that the buffer containing two fields is a The presence of the GST_VIDEO_FLAG_INTERLACED means that the buffer is an
progressive frame. The implication is that if this flag is not set, the buffer 'interlaced' or 'mixed' buffer that contains two fields that, when combined
is an 'interlaced' or 'mixed' buffer that contains two fields that, when with fields from adjacent buffers, allow reconstruction of progressive frames.
combined with fields from adjacent buffers, allow reconstruction of progressive The absence of the flag implies the buffer containing two fields is a
frames. progressive frame.