[FFmpeg-trac] #963(avcodec:new): [PATCH] Fraps: restore old behavior regarding P frames
FFmpeg
trac at avcodec.org
Tue Jan 31 21:00:39 CET 2012
#963: [PATCH] Fraps: restore old behavior regarding P frames
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Reporter: STaRGaZeR | Type: defect
Status: new | Priority: normal
Component: avcodec | Version: git-master
Keywords: fraps | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Recently there have been several commits by Reimar changing the Fraps
decoder behavior regarding P frames. These frames are not skip frames, but
repeat frames, as seen here
(http://wiki.multimedia.cx/index.php?title=Fraps) and confirmed by looking
at the reference decoder's output. Since Fraps is both a screen capture
codec and a CFR codec, when it records something with a refresh rate
slower than the target fps specified in its settings it adds these repeat
frames to achieve the target framerate.
By removing reget_buffer and outputting nothing when a P frame is reached,
the decoder is now VFR and not compliant because of the reasons explained
above. There can be files with 1 I frame at the beginning and the rest
being P frames, in this situation ffmpeg now outputs only 1 frame for the
entire duration of the video. I've been talking to Reimar, but he thinks
that since visually a repeated frame and a skip frame are the same, the
current behavior is correct. I've written a patch that fixes the
regression by outputting these repeated frames when it should as before,
but needs review as the changes required to do this and MT at the same
time are big.
When frame multithreading reget_buffer cannot be used, so in order to have
the previous frame available when a repeat frame comes, a 2 frame buffer
is used: the current one and the previous one. This implementation of MT
is almost the same as the one used in the mimic decoder.
frapsMTv2.patch is attached.
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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/963>
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