[mythtv-commits] Ticket #12728: Mythtranscode reporting incorrect audio properties

MythTV noreply at mythtv.org
Thu Apr 14 17:46:11 UTC 2016


#12728: Mythtranscode reporting incorrect audio properties
-----------------------------------------+---------------------------------
     Reporter:  JP Briggs <jp.briggs@…>  |      Owner:  jyavenard
         Type:  Bug Report - General     |     Status:  new
     Priority:  minor                    |  Milestone:  unknown
    Component:  MythTV - Mythtranscode   |    Version:  0.27.6
     Severity:  medium                   |   Keywords:  mythtranscode audio
Ticket locked:  0                        |
-----------------------------------------+---------------------------------
 I have a recording I am trying to transcode lossless to strip commercials.
 From there, I will re-encode using HandBrake.

 The original recording's audio is reported thusly (via mediainfo)


 {{{
 Audio #1
 ID                                       : 6302 (0x189E)
 Menu ID                                  : 1 (0x1)
 Format                                   : AC-3
 Format/Info                              : Audio Coding 3
 Mode extension                           : CM (complete main)
 Format settings, Endianness              : Big
 Codec ID                                 : 129
 Duration                                 : 35mn 58s
 Bit rate mode                            : Constant
 Bit rate                                 : 384 Kbps
 Channel(s)                               : 6 channels
 Channel positions                        : Front: L C R, Side: L R, LFE
 Sampling rate                            : 48.0 KHz
 Bit depth                                : 16 bits
 Compression mode                         : Lossy
 Delay relative to video                  : -562ms
 Stream size                              : 98.8 MiB (2%)
 Language                                 : English
 }}}

 I use mythtranscode from the CLI, and created the transcoded video thusly:
 {{{
 mythtranscode --chanid 1577 --starttime 20160327135900 --mpeg2
 --honorcutlist -e ts --passthrough -o ~/tmp/myrecording.mpg
 }}}

 The audio of the resultant file (mediainfo):
 {{{
 Audio #1
 ID                                       : 4301 (0x10CD)
 Menu ID                                  : 1 (0x1)
 Format                                   : AC-3
 Format/Info                              : Audio Coding 3
 Mode extension                           : CM (complete main)
 Format settings, Endianness              : Big
 Codec ID                                 : 129
 Duration                                 : 24mn 29s
 Bit rate mode                            : Constant
 Bit rate                                 : 192 Kbps
 Channel(s)                               : 2 channels
 Channel positions                        : Front: L R
 Sampling rate                            : 48.0 KHz
 Bit depth                                : 16 bits
 Compression mode                         : Lossy
 Delay relative to video                  : 8ms
 Stream size                              : 33.6 MiB (1%)
 Language                                 : English
 }}}

 Note the Channel(s) are reduced from 6 to 2, and the 'Bit rate' reduced to
 192Bkps from 384Kbps.

 This is, however, incorrect. Playing the transcoded file with VLC shows:
 {{{
        Type: Audio
 Original ID: 4301
       Codec: A52 Audio (aka AC3)(a52 )
    Language: Englisg
    Channels: 3F2R/LFE
 Sample rate: 48000 Hz
     Bitrate: 384 kb/s
 }}}

 Note that it IS actually 6 channel, 384Kbps. So the audio of the file is
 correct, but the descriptors in the TS container are incorrect.

 Unfortunately, when I open the transcoded file with HandBrake, HandBrake
 reports that the source audio is only 2 channel, and therefore cannot
 transcode to, e.g. AAC 6 channel; only 2.

--
Ticket URL: <https://code.mythtv.org/trac/ticket/12728>
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