Atmos substream recognized as AC3 stream?

[Samuel]

Summary of the bug:
How to reproduce:
When converting the audio stream n°1 to AC3 it produce a weird uniform audio stream like beeppp.
​https://www15.zippyshare.com/v/v5Nxi6Rm/file.html

% % ffmpeg.exe -i "dolby_EAC3_TrueHD_amaze_lossless-DWEU.m2ts" -map 0:V -map 0:a:1 -crf 23  -c:a ac3 -c:v libx264 -preset ultrafast convertionToAC3_defect.ts

[Samuel]

AC3_#7576

[Carl Eugen Hoyos]

Why do you believe there is a bug?

[Samuel]

Shouldn't this AC3 track have been showed?
The audio stream n°1 doesn't seem be a real one. I suspect it to be a substream.
The 0 and 2 seem correct audio streams.

[Carl Eugen Hoyos]

Replying to Sami32:

Shouldn't this AC3 track have been showed?

I believe the AC-3 track is shown correctly by current FFmpeg, but maybe I misunderstand?

$ ffmpeg -i dolby_EAC3_TrueHD_amaze_lossless-DWEU.m2ts
ffmpeg version N-92543-g8cc5107 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 6.4.0 (GCC)
  configuration: --enable-gpl --enable-libxml2 --enable-gnutls
  libavutil      56. 24.101 / 56. 24.101
  libavcodec     58. 40.100 / 58. 40.100
  libavformat    58. 23.100 / 58. 23.100
  libavdevice    58.  6.100 / 58.  6.100
  libavfilter     7. 46.101 /  7. 46.101
  libswscale      5.  4.100 /  5.  4.100
  libswresample   3.  4.100 /  3.  4.100
  libpostproc    55.  4.100 / 55.  4.100
Input #0, mpegts, from 'dolby_EAC3_TrueHD_amaze_lossless-DWEU.m2ts':
  Duration: 00:01:03.52, start: 4200.000000, bitrate: 22899 kb/s
  Program 1
    Stream #0:0[0x1011](eng): Video: h264 (High) (HDMV / 0x564D4448), yuv420p(progressive), 1920x1080, 24 fps, 24 tbr, 90k tbn, 48 tbc
    Stream #0:1[0x1100]: Audio: truehd (AC-3 / 0x332D4341), 48000 Hz, 7.1, s32 (24 bit)
    Stream #0:2[0x1100]: Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, 5.1(side), fltp, 640 kb/s
    Stream #0:3[0x1101]: Audio: eac3 (AC-3 / 0x332D4341), 48000 Hz, 7.1, fltp, 1664 kb/s
At least one output file must be specified

The audio stream n°1 doesn't seem be a real one.

What is not real about what audio stream?

I suspect it to be a substream.

Yes, I believe the AC-3 tracks that come with every TrueHD track on a Bluray are called substreams.

The 0 and 2 seem correct audio streams.

What makes an audio stream correct or incorrect in this context?

[Samuel]

Maybe i'm the one having misunderstood.

Stream #0:2[0x1100]: Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, 5.1(side), fltp, 640 kb/s

I don't see the use of such display, except if you like listen only a all long beeeeep song. It what i call incorrect. That said i could be wrong and it can have some use.

Here is what i consider a correct display:

General
ID                                       : 1 (0x1)
Complete name                            : F:\_DEVELOPPEMENT_TOOLS\!MEDIA_TEST_FILES\UMS Video Testing Suite (20150121)\TESTS\dolby_EAC3_TrueHD_amaze_lossless-DWEU.m2ts
Format                                   : BDAV
Format/Info                              : Blu-ray Video
File size                                : 173 MiB
Duration                                 : 1 min 3 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 22.9 Mb/s
Maximum Overall bit rate                 : 35.5 Mb/s

Video
ID                                       : 4113 (0x1011)
Menu ID                                  : 1 (0x1)
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4.1
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, RefFrames               : 4 frames
Codec ID                                 : 27
Duration                                 : 1 min 3 s
Bit rate mode                            : Variable
Bit rate                                 : 19.7 Mb/s
Maximum bit rate                         : 40.0 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 24.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.395
Stream size                              : 149 MiB (86%)
Language                                 : English

Audio #1
ID                                       : 4352 (0x1100)
Menu ID                                  : 1 (0x1)
Format                                   : AC-3 MLP FBA 16-ch
Format/Info                              : Audio Coding 3 + Meridian Lossless Packing FBA with 16-channel presentation
Commercial name                          : Dolby TrueHD with Dolby Atmos
Muxing mode                              : Stream extension
Codec ID                                 : 131
Duration                                 : 1 min 3 s
Bit rate mode                            : Variable
Bit rate                                 : 640 kb/s
Maximum bit rate                         : 9 096 kb/s
Channel(s)                               : 8 channels
Channel layout                           : L R C LFE Ls Rs Lb Rb
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Bit depth                                : 16 bits
Compression mode                         : Lossy
Stream size                              : 4.84 MiB (3%)
Service kind                             : Complete Main
Number of dynamic objects                : 15
Bed channel count                        : 1 channel
Bed channel configuration                : LFE

Audio #2
ID                                       : 4353 (0x1101)
Menu ID                                  : 1 (0x1)
Format                                   : E-AC-3
Format/Info                              : Enhanced AC-3
Commercial name                          : Dolby Digital Plus
Format profile                           : Blu-ray Disc
Muxing mode                              : Stream extension
Codec ID                                 : 132
Duration                                 : 1 min 3 s
Bit rate mode                            : Constant
Bit rate                                 : 1 664 kb/s
Channel(s)                               : 8 channels
Channel layout                           : L R C LFE Ls Rs Lb Rb
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Stream size                              : 12.6 MiB (7%)
Service kind                             : Complete Main

[Carl Eugen Hoyos]

I believe it is better to close this ticket.

[Samuel]

Hum...i suspect that the wrongly called AC3 stream is in fact only an Atmos substream not playable for itself.

[Hendrik]

Every TrueHD stream on Blu-ray discs has a AC3 substream. avformat exposes it as a separate stream so you can actually extract it. It has nothing to do with Atmos.

[Samuel]

Excuse my ignorance. I didn't knew that AC-3 could be a substream and again less that it could be unlistenable.

Thank you for sharing your knowledge.

[Balling]

Replying to Samuel:

Excuse my ignorance. I didn't knew that AC-3 could be a substream and again less that it could be unlistenable.

Thank you for sharing your knowledge.

No, it is listenable, usually. Except for Dolby demo disk of March 2018. It has Atmos EAC3 sound without independent ac3 track (that track is present though but decodes to speach that says that this is not an atmos track):

[eac3 @ 000001320d0f4480] Ignoring dependent frame without independent frame.

and one more Ac3 track inside TrueHD that is also just speach.