Support >6 channels in E-AC-3 audio encoder

[Ridley Combs]

E-AC-3 supports up to 15 full-bandwidth channels, but libavcodec's encoder currently doesn't support 6.1 and 7.1 channel layouts. Do these layouts just need to be added to ff_ac3_channel_layouts, or would this require additional work on the encoder?

[LigH]

This does not only belong to the E-AC-3 encoder, but also to the decoder or the format recognition in general. There is a report in the German doom9/Gleitz video forum that ffmpeg does not even recognize a 7.1 channel Blu-ray audio stream correctly, which consists of a 5.1 AC-3 core and additional E-AC-3 channels. It may have been related to a slightly older version; a rather current ffmpeg version (N-81308-g369ed11, 2016-08-09) prints a warning that it will handle only the 5.1 core:

[eac3 @ 0000000002a8f900] Dependent substream decoding is not implemented. Update your FFmpeg version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
[eac3 @ 0000000002a8f900] If you want to help, upload a sample of this file to ftp://upload.ffmpeg.org/incoming/ and contact the ffmpeg-devel mailing list. (ffmpeg-devel@ffmpeg.org)

Possibly relevant: MediaInfo does not recognize it correctly either (e.g. reports an obviously improbable bitrate of 500 bytes per second).

[LigH]

7.1 channel Blu-ray E-AC-3 with 5.1 AC-3 core and 2 dependent substreams

[Carl Eugen Hoyos]

Is this the one sample we know about (from a demo disk) or a new file?

[LigH]

AFAIK it's a new file, extracted from a Blu-ray by a Gleitz forum member.

​http://forum.gleitz.info/showthread.php?47670-e-ac3-richtig-convertieren

[Carl Eugen Hoyos]

Then please ask for a longer sample that provides actual audible sound (at least 2,5M) and ask which Bluray this is.

[Carl Eugen Hoyos]

Two minute eac3 7.1 sample (that does not come from the demo disk) uploaded to ​http://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket3595/

[dcxero]

Replying to LigH:

Possibly relevant: MediaInfo does not recognize it correctly either (e.g. reports an obviously improbable bitrate of 500 bytes per second).

MediaInfo only seems to have a bug reading 7.1 Dolby Digital Plus tracks authored using the Blu-ray Disc profile (which is what the other samples use). It can read 7.1 Dolby Digital Plus tracks authored using the standard profile (which is used more for software and file/streaming distribution)

Here is a Standard profile 7.1 sample: ​https://www.datafilehost.com/d/ae18d85c

[ackbc]

ffmpeg doesn't support encode 7.1 files into 7.1 EAC3

i've uploaded some samples for testing (three 7.1 files), i hope it could support 7.1 EAC3 encode, input output
the closed, dupe ticket ​https://trac.ffmpeg.org/ticket/8519

update: samples uploaded here.

[Nomis101]

This is also an annoying issue for HandBrake: ​https://github.com/HandBrake/HandBrake/issues/1085
What makes it so difficult to support >6 channels for E-AC3 encoding?

[richardpl]

Missing actual sponsor.

[Nomis101]

Replying to richardpl:

Missing actual sponsor.

Thats all? How to find a sponsor? Who can be a sponsor?

[richardpl]

The one with lot of money.

[LigH]

They possibly mean: someone willing to pay for access to confidential specifications, level "trade secret, and we have lawyers to protect it".

[richardpl]

Nope, look what I said and please stop spreading false information.

[Jim DeLaHunt]

Replying to richardpl:

Nope, look what I said and please stop spreading false information.

I'm new to the ticket. @richardpl, I'm afraid your comment:14 is a bit too cryptic for me to understand, especially given how in comment:18 you seem to say that the interpretation in comment:17 is "false information".

Could you please say clearly what you mean by "missing actual sponsor"? What does the sponsor do with their "lot of money"? Who do they give it to? How does it help?

It seems to me that part of what that money would do is pay for access to specifications. But you apparently don't mean that. Maybe it would pay a competent developer to write the necessary code? What do you mean, please?

[richardpl]

It means to write code. Specification is already available.

[LigH]

Regarding code, I would call that rather "contributor" than "sponsor". Hence the misunderstanding, maybe... contributing code is hopefully not bound to huge amounts of money. At least I wish.

[richardpl]

If you want to contribute code and time without any compensation, be my guest.

[tmchow]

Is this fixed now because #4608 was fixed? Or is the 8 channel fix in #4608 something unique that doesn't help 7 channel?

[Nomis101]

Replying to tmchow:

Is this fixed now because #4608 was fixed?

No, it is not. This is about encoder, #4608 is about decoder.

[tmchow]

Replying to Nomis101:

Replying to tmchow:

Is this fixed now because #4608 was fixed?

No, it is not. This is about encoder, #4608 is about decoder.

Ah, got it! thanks.