Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Andrew Sun]

Andrew Sun  gmail.com> writes:

> 
> Phil Rhodes  rocketmail.com> writes:
> 
> > 
> > > It would also have to be tested against the hardware TV Dolby 
> Vision> decoders for conformance.
> > It strikes me that if we could find examples of material that was 
> available in both Vision and other HDR
> > formats (HLG, HDR10 etc) for which the specs are open, a stab could be 
> made at a reasonably accurate
> > approach to transcoding.
> > It further strikes me that ffmpeg could also create MaxFALL and MaxCLL 
> metadata if it wanted to.
> > P
> 
> You're right about the last point. When FFmpeg is compiled with the
> external x265 library, it can encode HEVC not just with MaxFALL and
> MaxCLL, but also with SMPTE ST 2086 Metadata, to conform to the HDR10
> Media profile. FFmpeg I think can also decode HDR10 Metadata.
> 
> But we need to know how to implement the Dolby Vision decoder to decode 
> the full Dolby Vision bitstreams (both single layer and dual layer)
> without errors to silence.

Just did more research on Dolby Vision via the official website.
On Dolby's website, they have some PDFs about Dolby Vision. It can be
encoded and decoded through dual layer and single layer methods using
HEVC. Will have to contact them for more info.

Andrew Sun
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Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Andrew Sun]

Phil Rhodes  rocketmail.com> writes:

> 
> > It would also have to be tested against the hardware TV Dolby 
Vision> decoders for conformance.
> It strikes me that if we could find examples of material that was 
available in both Vision and other HDR
> formats (HLG, HDR10 etc) for which the specs are open, a stab could be 
made at a reasonably accurate
> approach to transcoding.
> It further strikes me that ffmpeg could also create MaxFALL and MaxCLL 
metadata if it wanted to.
> P

You're right about the last point. When FFmpeg is compiled with the
external x265 library, it can encode HEVC not just with MaxFALL and
MaxCLL, but also with SMPTE ST 2086 Metadata, to conform to the HDR10
Media profile. FFmpeg I think can also decode HDR10 Metadata.

But we need to know how to implement the Dolby Vision decoder to decode 
the full Dolby Vision bitstreams (both single layer and dual layer)
without errors to silence.

Andrew Sun
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Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Phil Rhodes]

> It would also have to be tested against the hardware TV Dolby Vision> 
>decoders for conformance.
It strikes me that if we could find examples of material that was available in 
both Vision and other HDR formats (HLG, HDR10 etc) for which the specs are 
open, a stab could be made at a reasonably accurate approach to transcoding.
It further strikes me that ffmpeg could also create MaxFALL and MaxCLL metadata 
if it wanted to.
P
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Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Andrew Sun]

Phil Rhodes  rocketmail.com> writes:

> 
> > It should be added that both avc and hevc support 12bit 
> > encoding...
> It's a bit more complicated than just a twelve-bit video signal. Vision 
uses the 10-bit image as a base and
> then trims it using the additional data stream, taking into account the 
capabilities of the display.
> Correct display would require knowledge of the capabilities of the 
display hardware itself, not to
> mention significant reverse-engineering of Dolby's engineering approach. 
Most Vision decoders will
> be built into displays and therefore have that knowledge.
> Decoding of Vision to the point where it could be transcoded into other 
HDR formats is possibly more
> feasible based on the standards for those formats.
> P  

I agree. Somehow the Dolby Vision decoder that would be built into
FFmpeg would need to auto-detect the hardware capabilities of the monitor.

It would also have to be tested against the hardware TV Dolby Vision
decoders for conformance.

Andrew Sun
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Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Phil Rhodes]

> It should be added that both avc and hevc support 12bit 
> encoding...
It's a bit more complicated than just a twelve-bit video signal. Vision uses 
the 10-bit image as a base and then trims it using the additional data stream, 
taking into account the capabilities of the display.
Correct display would require knowledge of the capabilities of the display 
hardware itself, not to mention significant reverse-engineering of Dolby's 
engineering approach. Most Vision decoders will be built into displays and 
therefore have that knowledge.
Decoding of Vision to the point where it could be transcoded into other HDR 
formats is possibly more feasible based on the standards for those formats.
P  
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Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Andrew Sun]

Carl Eugen Hoyos  ag.or.at> writes:

> 
> Andrew Sun  gmail.com> writes:
> 
> > https://drive.google.com/file/d/0B5-q6qHXjH0GcHNhT0g3aWxuNWM
> 
> I opened ticket #5688, thank you for the sample!
> 
> Is there a software decoder?
> Contrary to what was written, I think this would not be too 
> difficult if it were known what the additional nal's contain.
> 
> It should be added that both avc and hevc support 12bit 
> encoding...
> 
> Please avoid top-posting here, it is considered rude.
> 
> Carl Eugen

I looked online, and could not find a Dolby Vision
software decoder.

We would probably need a hardware decoder built into a
TV such as the Dolby Vision enabled LG E6.

Andrew Sun

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Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Carl Eugen Hoyos]

Andrew Sun  gmail.com> writes:

> https://drive.google.com/file/d/0B5-q6qHXjH0GcHNhT0g3aWxuNWM

I opened ticket #5688, thank you for the sample!

Is there a software decoder?
Contrary to what was written, I think this would not be too 
difficult if it were known what the additional nal's contain.

It should be added that both avc and hevc support 12bit 
encoding...

Please avoid top-posting here, it is considered rude.

Carl Eugen

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Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Andrew Sun]

Maybe it can be made as a FFmpeg Google Summer of Code 2017 mentored
project.

But now I can see how much time and money it would need to develop
something that big. A dual layer decoder and HDR dynamic metadata support
has never been implemented in FFmpeg before. We would need to implement the
VES splitter that combines the decoders, dynamic metadata parser, the Dolby
Vision composer that combines the base bitstream and metadata, and possibly
the display management.

Dolby Vision uses not only the YCbCr color format, but also ICtCp, which is
a color format designed by Dolby for HDR and Wide Color Gamuts. We would
also need to include support for ICtCp and its pixel formats (e.g. itp420p,
itp420p10, etc.).

I think that we can wait for a while before implementing a Dolby Vision
decoder. After all, there are currently no Ultra-HD Blu-rays in the store
that are Dolby Vision enabled. Also, I'm pretty sure since Dolby Vision is
proprietary, there would have to be reverse engineering involved.

Andrew Sun

On Sat, Jul 2, 2016 at 5:59 AM, Phil Rhodes <phil_rho...@rocketmail.com>
wrote:

> That's a very, very big job which I suspect won't be happening without
> significant amounts of financial input.
> P
>
>
>   From: Carl Eugen Hoyos <ceho...@ag.or.at>
>  To: ffmpeg-user@ffmpeg.org
>  Sent: Saturday, 2 July 2016, 8:35
>  Subject: Re: [FFmpeg-user] feature request/suggestion: add support for
> dolby vision decoding :)
>
> Andrew Sun  gmail.com> writes:
>
> > Dolby Vision is a 12-bit HDR dual layer codec that has a 10-bit
> > base layer of either HEVC or AVC, and then an enhancement layer
> > that supplies an extra 2-bits and dynamic HDR metadata.
>
> Please provide a sample.
>
> Carl Eugen
>
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Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Phil Rhodes]

That's a very, very big job which I suspect won't be happening without 
significant amounts of financial input.
P


  From: Carl Eugen Hoyos <ceho...@ag.or.at>
 To: ffmpeg-user@ffmpeg.org 
 Sent: Saturday, 2 July 2016, 8:35
 Subject: Re: [FFmpeg-user] feature request/suggestion: add support for dolby 
vision decoding :)
   
Andrew Sun  gmail.com> writes:

> Dolby Vision is a 12-bit HDR dual layer codec that has a 10-bit 
> base layer of either HEVC or AVC, and then an enhancement layer 
> that supplies an extra 2-bits and dynamic HDR metadata.

Please provide a sample.

Carl Eugen

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Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Andrew Sun]

https://drive.google.com/file/d/0B5-q6qHXjH0GcHNhT0g3aWxuNWM/view?usp=sharing

Here is the link to the Dolby Vision sample. Unfortunately, it will only
play correctly on a Dolby Vision enabled TV. Most TVs and all media players
will simply discard the enhancement layer when decoding, leaving only the
base layer.

Andrew Sun

On Sat, Jul 2, 2016 at 3:35 AM, Carl Eugen Hoyos  wrote:

> Andrew Sun  gmail.com> writes:
>
> > Dolby Vision is a 12-bit HDR dual layer codec that has a 10-bit
> > base layer of either HEVC or AVC, and then an enhancement layer
> > that supplies an extra 2-bits and dynamic HDR metadata.
>
> Please provide a sample.
>
> Carl Eugen
>
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Re: [FFmpeg-user] feature request/suggestion: add support for dolby vision decoding :)

[Carl Eugen Hoyos]

Andrew Sun  gmail.com> writes:

> Dolby Vision is a 12-bit HDR dual layer codec that has a 10-bit 
> base layer of either HEVC or AVC, and then an enhancement layer 
> that supplies an extra 2-bits and dynamic HDR metadata.

Please provide a sample.

Carl Eugen

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