[mythtv-commits] Ticket #11639: Audio lost after transcode

MythTV noreply at mythtv.org
Thu Jul 4 11:58:17 UTC 2013


#11639: Audio lost after transcode
------------------------------------+----------------------------
 Reporter:  oli.henning@…           |          Owner:
     Type:  Bug Report - General    |         Status:  new
 Priority:  major                   |      Milestone:  unknown
Component:  MythTV - Mythtranscode  |        Version:  0.26-fixes
 Severity:  medium                  |     Resolution:
 Keywords:  transcode audio         |  Ticket locked:  0
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Comment (by oli.henning@…):

 Just to help, as far as i can:

 I did some further analyzes with the tool {{{tsinfo}}} (from the
 {{{tstools}}}-Package):

 Problematic recording (audio lost after transcode):
 {{{
 Packet 1 is PAT
 Program list:
     Program 1 -> PID 00a4 (164)

 Packet 2 is PMT with PID 00a4 (164)
   Program 1, version 12, PCR PID 0090 (144)
   Program streams:
     PID 0090 ( 144) -> Stream type 02 (  2) H.262/13818-2 video (MPEG-2)
 or 11172-2 constrained video
         ES info (3 bytes): 52 01 01
         Descriptor tag 52 ( 82) (1 byte): 01
     PID 0091 ( 145) -> Stream type 03 (  3) 11172-3 audio (MPEG-1)
         ES info (9 bytes): 52 01 02 0a 04 67 65 72 01
         Descriptor tag 52 ( 82) (1 byte): 02
         Languages: ger/clean effects
     PID 0092 ( 146) -> Stream type 03 (  3) 11172-3 audio (MPEG-1)
         ES info (9 bytes): 52 01 03 0a 04 65 6e 67 01
         Descriptor tag 52 ( 82) (1 byte): 03
         Languages: eng/clean effects
     PID 009b ( 155) -> Stream type 81 (129) User private
         ES info (12 bytes): 6a 01 00 52 01 05 0a 04 67 65 72 01
         DVB AC-3 (1 byte): 00
         Descriptor tag 52 ( 82) (1 byte): 05
         Languages: ger/clean effects
     PID 00ae ( 174) -> Stream type 06 (  6) H.222.0/13818-1 PES private
 data (maybe Dolby/AC-3 in DVB)
         ES info (15 bytes): 52 01 04 56 0a 67 65 72 09 00 67 65 72 17 77
         Descriptor tag 52 ( 82) (1 byte): 04
         Teletext: language=ger, type=Initial, magazine 1, page 0
                   language=ger, type=Subtitles, magazine 7, page 77
 }}}
 To compare: A non-problematic recording (of another channel):
 {{{
 Packet 1 is PAT
 Program list:
     Program 1 -> PID 02e4 (740)

 Packet 2 is PMT with PID 02e4 (740)
   Program 1, version 2, PCR PID 02d0 (720)
   Program streams:
     PID 02d0 ( 720) -> Stream type 02 (  2) H.262/13818-2 video (MPEG-2)
 or 11172-2 constrained video
         ES info (3 bytes): 52 01 01
         Descriptor tag 52 ( 82) (1 byte): 01
     PID 02d1 ( 721) -> Stream type 03 (  3) 11172-3 audio (MPEG-1)
         ES info (9 bytes): 0a 04 64 65 75 01 52 01 03
         Languages: deu/clean effects
         Descriptor tag 52 ( 82) (1 byte): 03
     PID 02db ( 731) -> Stream type 81 (129) User private
         ES info (16 bytes): 6a 05 ff 42 08 00 00 0a 04 64 65 75 01 52 01
 07
         DVB AC-3 (5 bytes): ff 42 08 00 00
         Languages: deu/clean effects
         Descriptor tag 52 ( 82) (1 byte): 07
     PID 02ee ( 750) -> Stream type 06 (  6) H.222.0/13818-1 PES private
 data (maybe Dolby/AC-3 in DVB)
         ES info (15 bytes): 52 01 0a 56 0a 64 65 75 09 00 64 65 75 11 49
         Descriptor tag 52 ( 82) (1 byte): 0a
         Teletext: language=deu, type=Initial, magazine 1, page 0
                   language=deu, type=Subtitles, magazine 1, page 49
 }}}
 == Analyze details ==
 - Each of the first audio-stream has another value "descriptor tag 52"
 - The ordering of the Descriptor-Tags in the "ES info" (of the audio-
 stream) is different: In one problematic case, it's tag "0x52" followed by
 tag "0x0A". In the non-prblematic-case case it's the other way around.
 - The ISO language-codes are different. In one case it's "deu" (for
 "deutsch"). In the other case it's "ger" (for "german")
 - number of audio-channels are different: the 'problematic' recording hat
 3 audio-streams (2*MP2 and 1*AC3) and the non-problematic just hast two
 (1*MP2 and 1*AC3)
 - The PID-Values differ
 == My conclution ==
 These differences in the DVB-meta-data (PAT, PMT, PID-Numbers and number
 of audio-channels) seems very trivial to me so i think that this is not
 the cause of the "audio lost problem"
 So the problem is probably within the audio-elementary-streams themselve.
 Or it's a specific TS-packet-multiplexing case which could not be handled
 by mythtranscode/ffmpeg.

--
Ticket URL: <http://code.mythtv.org/trac/ticket/11639#comment:1>
MythTV <http://www.mythtv.org>
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