[FFmpeg-devel] Playback issue on Sony TVs caused by btrt box

[Jan Ekström]

On Mon, Feb 21, 2022 at 5:07 PM Eran Kornblau <eran.kornblau at kaltura.com> wrote:
>
> Hi all,
>
> We've recently upgraded our ffmpeg version, and we got a playback issue on some Sony TV models that are playing HBBTV/DASH+DRM - video plays fine, audio doesn't play at all.
> Listing here some of the affected models (not pasting all, the list is long...) - KDL-32W600D, KDL-40W650D, KDL-48W650D, KDL-43W750D, KDL-49W750D, KDL-55W650D.
>
> After some investigation, we found the cause was the addition of the 'btrt' atom to the mp4 –
> https://github.com/FFmpeg/FFmpeg/commit/3838e8fc210aa09a9f9058506c0ce80b6ad9b9c3
> The TV decoder expects to get the sinf atom right after esds, and doesn't properly handle the btrt atom in between
> (our packager adds the sinf atom at the end of the original stsd entry that was read from the mp4 file).
>
> Since, in my understanding, the btrt atom was added mostly for reporting reasons, IMHO, it should be a config option - off by default.
> I would happily submit a patch for it, but sending this first, in case there are any concerns/objections.
>

In case the use case was unknown, the primary reason for adding this
was to utilize this box to inform a media server of an incoming live
stream's bit rate, since the overall bit rate cannot be calculated for
something that isn't done yet
(https://dashif-documents.azurewebsites.net/Ingest/master/DASH-IF-Ingest.html
as an example of one such use case). This being an alternative to
nonstandard things such as ISML manifests.

Additionally, since it seemed to be specified at the end of the given
structures, I added it at the end of these given boxes. Apparently
thus it made your live patching of that box no longer compatible with
these parsers, since you just append your required things to the end
of it. Am I understanding things correctly?

Jan