Atmos substream recognized as AC3 stream?

[Sami32]

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

[Sami32]

AC3_#7576

[cehoyos]

Why do you believe there is a bug?

[Sami32]

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

[cehoyos]

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?

[Sami32]

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

[cehoyos]

I believe it is better to close this ticket.

[Sami32]

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

[heleppkes]

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.

[Sami32]

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.