#2592: Bug with b-frames?
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Reporter: microchip | Owner:
Type: defect | Status: new
Priority: important | Component: avcodec
Version: git-master | Resolution:
Keywords: regression | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Comment (by microchip):
Hi Carl,
Thanks for the response. It produces a valid output but it's of low
quality compared to the output of 1.2.1. I contribute this to the 0
entries for b-frames (in: 0 and out: 0) in the log file I attached for the
git version. When I say low quality, I mean that I can see blocks all over
the place while when using 1.2.1 this is not the case. I no longer have
the film I used when I noticed this problem so I tried on a sample here
and the problem is the same.
About the bitrate, in 1.2.1 when using 4600k as bitrate, the second pass
would go up to 3000k while the git ffmpeg will go just over 1600k. That's
a pretty big difference between the two versions
The second pass output for the sample I tried is as follows:
{{{
ffmpeg version N-53304-g2187600 Copyright (c) 2000-2013 the FFmpeg
developers
built on May 20 2013 19:53:33 with gcc 4.7 (SUSE Linux)
configuration: --enable-shared --enable-gpl --enable-version3 --enable-
libx264 --enable-libxvid --enable-libmp3lame --enable-avresample
--prefix=/home/neutrino/local
libavutil 52. 33.100 / 52. 33.100
libavcodec 55. 10.101 / 55. 10.101
libavformat 55. 7.100 / 55. 7.100
libavdevice 55. 1.100 / 55. 1.100
libavfilter 3. 68.101 / 3. 68.101
libavresample 1. 1. 0 / 1. 1. 0
libswscale 2. 3.100 / 2. 3.100
libswresample 0. 17.102 / 0. 17.102
libpostproc 52. 3.100 / 52. 3.100
[mpeg @ 0xff89c0] max_analyze_duration 5000000 reached at 5000000
microseconds
Guessed Channel Layout for Input Stream #0.1 : stereo
Input #0, mpeg, from '/home/neutrino/file2dvd/jlo/tmp22404.mpg':
Duration: 00:05:12.91, start: 0.280000, bitrate: 8234 kb/s
Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p, 720x576 [SAR
16:15 DAR 4:3], 25 fps, 25 tbr, 90k tbn, 50 tbc
Stream #0:1[0xa0]: Audio: pcm_s16be, 48000 Hz, stereo, s16, 1536 kb/s
[mpeg2video @ 0xffaa20] [lavc rc] Using all of requested bitrate is not
necessary for this video with these parameters.
[dvd @ 0xffa140] VBV buffer size not set, muxing may fail
Output #0, dvd, to '/home/neutrino/file2dvd/jlo/jlo.mpg':
Metadata:
encoder : Lavf55.7.100
Stream #0:0: Video: mpeg2video, yuv420p, 720x576 [SAR 16:15 DAR 4:3],
q=2-31, pass 2, 8000 kb/s, 90k tbn, 25 tbc
Stream #0:1: Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (mpeg2video -> mpeg2video)
Stream #0:1 -> #0:1 (pcm_s16be -> ac3)
Press [q] to stop, [?] for help
[mpeg2video @ 0xff9340] warning: first frame is no keyframe
Last message repeated 1 times
}}}
How to reproduce: just compile latest git and use -bf 2 for encoding. Then
look at the log file and you'll see that all "type: 3" entries have "in:
0" and "out: 0" entries. Then look at the output file and you'll see
blocks all over the place. At least this is the case here when comparing
to the 1.2.1 version
--
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2592#comment:2>
FFmpeg <http://ffmpeg.org>
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