[FFmpeg-devel] Enquiry re resolving errors reported by stream analysers after transcoding with FFmpeg

[Michael Niedermayer]

Hi

On Thu, Oct 25, 2018 at 08:36:26AM +0000, Stephenson, Angelica wrote:
> Hello,
> 
> I’m emailing to seek your advice. For the past few months, a team here at Sky UK has performed testing to determine whether FFmpeg would be a suitable transcode resource for a variety of use cases. Some tests failed due to stream analysers reporting errors, summary listed below. What would be required to make a sensible and indicative estimate on cost and level of effort required for you or someone in your team to resolve the errors being reported?
> 
> Errors reported by analysers
> 
>   *   Unable to insert PCR on PES (TR-8 requirement from Sky's VRP video spec for PDL)
>   *   MPEG and AAC audio buffer overflows (Manzanita)
>   *   PES header data_alignment_indicator flag not set for video and audio (Manzanita)
>   *   Failed HRD conformance check (Tektronix Cerify)
>   *   TB overflows (A/V Codec Analyser)
>   *   PTS (Presentation Timestamp) interval is not constant in audio stream (A/V Codec Analyser)
>   *   PTS must occur after end of Access Unit (A/V Codec Analyser)
>   *   PCR discontinuities (A/V Codec Analyser)

reproducable testcases would very usefull.
Iam sure there are bugs in our mpeg ts muxer but possibly some of these are also just
configuration issues.

More generally and a maybe this is a little bit a rant ;)
If all these slightly expensive Analysers would have been available to the
wider community then the developers who worked on the related code would
have been aware of the problems with details and would have been able to fix these when
the code was originally written or at least long ago.
As it is, its not unknown there are problems in the code but with no details
and no easy way to test potential fixes, its not so easy to fix for many
developers. There may be a very small number of developers who know mpeg-ts
so well they can understand and fix bugs without any way to test but i think
there are many more people who have a more shallow understaning and who have
more time who could with detailed information of what is wrong and with the
ability to test changes be able to fix these as well

I hope my slightly random comment helps
Iam not sure i have enough time to work on these myself but i would possibly
be in principle be interrested to try/play with fixing some of these if there
maybe was some sort of bounty on a working fix for each and i wouldnt have to 
commit myself to fixing it. mpeg-ts is not exactly my most favorite format and
some of these might be non trivial or end up requiring large scale changes, 
i am also no mpeg-ts expert, i know the format only approximatly.
Thats just my personal view, iam sure others have other views about mpeg-ts,
our (buggy) implementation and how to best improve it. 
I do not know if theres someone who knows mpeg-ts well, has plenty of time
and wants to fix all the issues. But if so, that would of course be best.

Thanks

> 
> Thanks in advance,
> Angelica.
> 
> Angelica Stephenson
> Senior Technical Lead
> 
> Sky UK
> Tel:   +44 (0) 7596 352 078
> Email:angelica.stephenson at sky.uk<mailto:angelica.stephenson at sky.uk>
> Website:www.sky.com<blocked::blocked::http://www.sky.com/>
> 
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