[mythtv-users] Encoding to h264 Some Recordings Have No Sound

Ian Barton lists at manor-farm.org
Wed Dec 30 08:46:46 UTC 2009

I have been transcoding stuff to h264 for months. However recently some 
transcodes are producing videos with no sound. I can't seem to find the 
reason for this. I am using ffmpeg built from svn. I have reverted to a 
version of ffmpeg that I know worked before with no luck.

This happens even with different series recorded from the same channel, 
which I would expect to have the same video profile. Here is a sample 
showing my ffmpeg encoding and its output. I have tried tweaking the 
various audio output params to no effect:

/usr/bin/nice -19 ffmpeg -y -i /home/mythmedia/1020_20091217095900.mpg 
-f mp4 -vcodec libx264 -r 30 -s 320x240 -qcomp 0.6 -qmin 11 -qmax 51 
-qdiff 4 -flags +loop -cmp +chroma -subq 7 -refs 6 -g 250 -keyint_min 25 
-rc_eq "blurCplx^(1-qComp)" -sc_threshold 40 -me_range 12 -i_qfactor 
0.71 -directpred 3 -f mp4 -threads 4 -acodec libfaac -ar 22050 -ab 64k 
-ac 2 -async 1 -crf 26 -aspect 4:3 

Input #0, mpeg, from '/home/mythmedia/1020_20091217095900.mpg':
   Duration: 00:30:44.04, start: 0.360000, bitrate: 1680 kb/s
     Stream #0.0[0x1e0]: Video: mpeg2video, yuv420p, 544x576 [PAR 24:17 
DAR 4:3], 15000 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
     Stream #0.1[0x1c0]: Audio: mp2, 48000 Hz, 1 channels, s16, 64 kb/s
     Stream #0.2[0x1c1]: Audio: mp2, 48000 Hz, 2 channels, s16, 128 kb/s
[libx264 @ 0x1549190]using SAR=1/1
[libx264 @ 0x1549190]using cpu capabilities: MMX2 SSE2Slow
[libx264 @ 0x1549190]profile Baseline, level 1.3
Output #0, mp4, to 
     Stream #0.0: Video: libx264, yuv420p, 320x240 [PAR 1:1 DAR 4:3], 
q=11-51, 200 kb/s, 30 tbn, 30 tbc
     Stream #0.1: Audio: aac, 48000 Hz, 1 channels, s16, 64 kb/s
Stream mapping:
   Stream #0.0 -> #0.0
   Stream #0.1 -> #0.1
Press [q] to stop encoding
frame= 1509 fps= 70 q=28.0 Lsize=    2216kB time=60.05 bitrate= 
video:2160kB audio:17kB global headers:0kB muxing overhead 1.824322%
[libx264 @ 0x1549190]frame I:18    Avg QP:23.71  size:  6385


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