[mythtv-commits] Ticket #11639: Audio lost after transcode
MythTV
noreply at mythtv.org
Tue Jul 2 21:33:00 UTC 2013
#11639: Audio lost after transcode
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Reporter: oli.henning@… | Type: Bug Report - General
Status: new | Priority: major
Milestone: unknown | Component: MythTV - Mythtranscode
Version: 0.26-fixes | Severity: medium
Keywords: transcode audio | Ticket locked: 0
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Since a few weeks i have a problem with mythtranscode:
Audio is completly lost after transcoding.
Perhaps this is the same or similar to
http://code.mythtv.org/trac/ticket/7118
== Details ==
- Recording with DVB-C
- Problem occurs just on one specific channel: "ORF 1" (prime channel of
austria).
- Recorded in switzerland, cable-provider "UPC Cablecom"
- Problem does not occur on every recording - so the problem is not
"stable"
- Just using "lossless MPEG-2" transcoding to cut-off commerials.
- No audio- and no video-recompression (so it's quite fast)
- Before the transcoding all audio-channels are present in mythfrontend
- Changes in audio-streams-combinations within recoding is recognized in
mythfrontend (e.g. not from the beginning but from somewhere in the middle
of the recoding there is an AC3-stream)
== Example-File to reproduce ==
https://dl.dropboxusercontent.com/u/517875/2109_20130701213000.mpg
I cutted of the first 310'200'000 Bytes. This are exactly 1'650'000 TS-
Packets (each 188 Bytes). So this is just the first ~9 minutes of the
original recording.
'''Interesting fact''': If the file would be just the first 1'600'000 TS-
Packets, then
{{{mythtranscode}}} will __not__ have the audio-loss-problem. This is the
reason why the test-file-to-reproduce has to be so big.
== LOG-Output of mythtranscode ==
{{{
(my_av_print) Input #0, mpegts, from
'/mnt/mythtvRecordings/2109_20130701213000.mpg':
(my_av_print) Duration: N/A, bitrate: N/A
(my_av_print) Stream #0:0[0x90]: Video: mpeg2video, 90k tbn
(my_av_print) Stream #0:1[0x91](ger): Audio: mp3, 0 channels
(my_av_print) Stream #0:2[0x9b](ger): Audio: ac3, 0 channels
(my_av_print) Stream #0:3[0xae](ger): Subtitle: dvb_teletext
(InitAV) Skipping invalid audio stream: 1
(InitAV) Skipping invalid audio stream: 2
}}}
You can see, that mythtranscode has some problems in identifying the
stream-content:
- mythtranscode could not detect the recording-duration (just logs "N/A")
- mythtranscode could not detect details of the video-stream (pixel-
format, frame-size, frame-rate, ...)
- mythtranscode detected the first audio-stream as beeing "mp3". But
actually it's a normal "mp2" audio-stream (analyzed with avprobe)
To compare: the log of a 'normal' transcoding:
{{{
(my_av_print) Input #0, mpegts, from
'/mnt/mythtvRecordings/2102_20130629193300.mpg':
(my_av_print) Duration: 00:44:56.88, start: 13209.723733, bitrate: 7099
kb/s
(my_av_print) Stream #0:0[0x50]: Video: mpeg2video (Main), yuv420p,
720x576 [SAR 64:45 DAR 16:9], 15000 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
(my_av_print) Stream #0:1[0x51](deu): Audio: mp2, 48000 Hz, stereo,
s16, 192 kb/s
(my_av_print) Stream #0:2[0x52](eng): Audio: mp2, 48000 Hz, stereo,
s16, 192 kb/s
(my_av_print) Stream #0:3[0x6e](deu): Data: dvb_vbi
(InitAV) Skipping unsupported codec 2 on stream 3
}}}
On request i can do further investigations. Perhaps you have to name me
some analyze-tools.
--
Ticket URL: <http://code.mythtv.org/trac/ticket/11639>
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