[MEncoder-users] Mpeg duration too short

[Peter B.]

Zitat von Carl Eugen Hoyos <cehoyos at ag.or.at>:

> Peter B. <pb <at> das-werkstatt.com> writes:
>
>> I'm using mencoder to generate DVD-conform MPEGs from lossless
>> FFv1/pcm_16sle AVI files. While doing so, I've realized that in 9/10
>> of all cases, the resulting mpegs are too short.
>
> Is this also reproducible with FFmpeg?

I've now tried with FFmpeg (git version: N-36728-g794006f), and the  
duration is fine - so it's mencoder-specific.

However, there's an interesting issue caused by FFmpeg: The first  
frame of the video is extremely ugly pixelated:
http://download.das-werkstatt.com/pb/mthk/examples/mencoder_mpeg/vx-04690_01-026s-ffmpeg.png

I assume this could be related by the "rc buffer underflow" warning?
The rest of the MPEG generated with FFmpeg is fine.


// -------------------------------
ffmpeg -i input/hires/vx-04690_01-026s.avi -target pal-dvd -vcodec  
mpeg2video -bufsize 1835k -maxrate 8000k -b:v 4000k -g 25 -vstrict 0  
-acodec ac3 -ab 192k out/026s-ffmpeg.mpg

ffmpeg version N-36728-g794006f Copyright (c) 2000-2012 the FFmpeg developers
   built on Jan 12 2012 09:16:04 with gcc 4.4.5
   configuration: --prefix=/usr/local --enable-gpl --enable-nonfree  
--enable-postproc --enable-swscale --enable-avfilter --enable-pthreads  
--enable-bzlib --enable-libmp3lame --enable-libvorbis --enable-libxvid  
--enable-zlib --enable-libopenjpeg --enable-decoder=png  
--enable-encoder=png --enable-libdirac --enable-libschroedinger
   libavutil      51. 34.100 / 51. 34.100
   libavcodec     53. 55.100 / 53. 55.100
   libavformat    53. 29.100 / 53. 29.100
   libavdevice    53.  4.100 / 53.  4.100
   libavfilter     2. 58.100 /  2. 58.100
   libswscale      2.  1.100 /  2.  1.100
   libswresample   0.  6.100 /  0.  6.100
   libpostproc    51.  2.100 / 51.  2.100
Input #0, avi, from 'input/hires/vx-04690_01-026s.avi':
   Metadata:
     encoder         : Lavf53.28.100
   Duration: 00:01:00.00, start: 0.000000, bitrate: 37457 kb/s
     Stream #0:0: Video: ffv1 (FFV1 / 0x31564646), yuv422p, 720x576,  
25 tbr, 25 tbn, 25 tbc
     Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz,  
2 channels, s16, 1536 kb/s
[buffer @ 0x9024c40] w:720 h:576 pixfmt:yuv422p tb:1/1000000 sar:0/1  
sws_param:
[buffersink @ 0x901cc40] auto-inserting filter 'auto-inserted scale 0'  
between the filter 'src' and the filter 'out'
[scale @ 0x901cfa0] w:720 h:576 fmt:yuv422p -> w:720 h:576 fmt:yuv420p  
flags:0x4
Incompatible sample format 's16' for codec 'ac3', auto-selecting format 'flt'
[ac3 @ 0x901b080] channel_layout not specified
[ac3 @ 0x901b080] No channel layout specified. The encoder will guess  
the layout, but it might be incorrect.
Output #0, dvd, to 'out/026s-ffmpeg.mpg':
   Metadata:
     encoder         : Lavf53.29.100
     Stream #0:0: Video: mpeg2video, yuv420p, 720x576, q=2-31, 4000  
kb/s, 90k tbn, 25 tbc
     Stream #0:1: Audio: ac3, 48000 Hz, stereo, flt, 192 kb/s
Stream mapping:
   Stream #0:0 -> #0:0 (ffv1 -> mpeg2video)
   Stream #0:1 -> #0:1 (pcm_s16le -> ac3)
Press [q] to stop, [?] for help
[mpeg2video @ 0x9017f80] rc buffer underflow
frame= 1500 fps= 24 q=2.0 Lsize=   30798kB time=00:00:59.96  
bitrate=4207.8kbits/s
video:28827kB audio:1406kB global headers:0kB muxing overhead 1.868384%