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ffmpeg: disable runtime frame rate changes support.

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This change was introduced by Colin for DVB-T support, however it also
breaks the timing of several MP4 files. The code is incomplete and
computes slightly to very wrong frame rates (one video plays about twice
as fast as needed, another one attempts to play at 30000 FPS).

I suspect similar problems would be found when changing the frame rate
in DVB-T streams in the same way, so I'm disabling this code for now
until a correct solution is found or we manage to use a newer version of
ffmpeg (where there is an actual framerate field in the format and it
doesn't need to be derived from the time_base anymore).

This restores the previous behavior of computing the framerate at the
AVFormatReader level, that is, once per stream, rather than once per
frame. At the stream level we have enough data to compute an "average"
frame rate, and there is also an "r_frame_rate" (real frame rate) which
may be usable for this. Not having working DVB-T hardware to experiment
with that yet, I'll leave it to others.

Fixes #11283 and the last remaining problem in #4512.
This commit is contained in:
Adrien Destugues 2014-12-09 15:42:49 +01:00
parent dca4966cd6
commit ff68ae9837
1 changed files with 35 additions and 6 deletions
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41
src/add-ons/media/plugins/ffmpeg/AVCodecDecoder.cpp
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@ -503,16 +503,45 @@ AVCodecDecoder::_NegotiateVideoOutputFormat(media_format* inOutFormat)
inOutFormat->u.raw_video = fInputFormat.u.encoded_video.output;
inOutFormat->u.raw_video.interlace = 1;
// Progressive (non-interlaced) video frames are delivered
inOutFormat->u.raw_video.first_active = fHeader.u.raw_video.first_active_line;
inOutFormat->u.raw_video.first_active
= fHeader.u.raw_video.first_active_line;
inOutFormat->u.raw_video.last_active = fHeader.u.raw_video.line_count;
inOutFormat->u.raw_video.pixel_width_aspect = fHeader.u.raw_video.pixel_width_aspect;
inOutFormat->u.raw_video.pixel_height_aspect = fHeader.u.raw_video.pixel_height_aspect;
inOutFormat->u.raw_video.pixel_width_aspect
= fHeader.u.raw_video.pixel_width_aspect;
inOutFormat->u.raw_video.pixel_height_aspect
= fHeader.u.raw_video.pixel_height_aspect;
#if 0
// This was added by Colin Günther in order to handle streams with a
// variable frame rate. fOutputFrameRate is computed from the stream
// time_base, but it actually assumes a timebase equal to the FPS. As far
// as I can see, a stream with a variable frame rate would have a higher
// resolution time_base and increment the pts (presentation time) of each
// frame by a value bigger than one.
//
// Fixed rate stream:
// time_base = 1/50s, frame PTS = 1, 2, 3... (for 50Hz)
//
// Variable rate stream:
// time_base = 1/300s, frame PTS = 6, 12, 18, ... (for 50Hz)
// time_base = 1/300s, frame PTS = 5, 10, 15, ... (for 60Hz)
//
// The fOutputFrameRate currently does not take this into account and
// ignores the PTS. This results in playing the above sample at 300Hz
// instead of 50 or 60.
//
// However, comparing the PTS for two consecutive implies we have already
// decoded 2 frames, which may not be the case when this method is first
// called.
inOutFormat->u.raw_video.field_rate = fOutputFrameRate;
// Was calculated by first call to _DecodeNextVideoFrame()
#endif
inOutFormat->u.raw_video.display.format = fOutputColorSpace;
inOutFormat->u.raw_video.display.line_width = fHeader.u.raw_video.display_line_width;
inOutFormat->u.raw_video.display.line_count = fHeader.u.raw_video.display_line_count;
inOutFormat->u.raw_video.display.bytes_per_row = fHeader.u.raw_video.bytes_per_row;
inOutFormat->u.raw_video.display.line_width
= fHeader.u.raw_video.display_line_width;
inOutFormat->u.raw_video.display.line_count
= fHeader.u.raw_video.display_line_count;
inOutFormat->u.raw_video.display.bytes_per_row
= fHeader.u.raw_video.bytes_per_row;
#ifdef TRACE_AV_CODEC
char buffer[1024];