Re: [Hls-interest] Image-based subtitles and trickplay tracks

Nicolas, Phil, all,
We (Comcast) would also gladly support including the trick play issue in
the RFC.
Best,
Alex.

On Thu, May 21, 2020 at 6:23 AM Phil Cluff <phil@mux.com> wrote:

> Hey Nicolas et al.
>
> I'd certainly lend my (and Mux's) support for the second of these in
> particular, a more elegant and interchangeable way to do trickplay would
> really go a long way in helping in architectures composed around
> just-in-time processing of media files.
>
> Thanks.
>
> On Wed, May 20, 2020 at 11:13 PM Weil, Nicolas <nicoweil@elemental.com>
> wrote:
>
>> Hello,
>>
>>
>>
>> We are often seeing two image-related topics causing interoperability
>> problems as they are not currently covered by the HLS spec. Normalizing the
>> implementations around an official specification for these two points would
>> be great:
>>
>>
>>
>> *Image-based subtitles tracks*
>> For workflow reasons and charset reasons, some content owners don't
>> include text-based subtitles in the live channels sources that they provide
>> to distributors, but rather image-based subtitles (like DVB-Sub). While
>> it's possible to transform these subtitles as IMSC1 Image Profile as per
>> DASH-IF IOP section 6.4.4, there is no equivalent IMSC1 Image Profile
>> support in the HLS RFC, which means that companies will continue to rely on
>> proprietary forks of the HLS RFC to support these use cases. Even if it
>> wasn't supported by Apple players, it would be tremendously helpful for
>> interoperability in the rest of the HLS ecosystem.
>>
>>
>>
>> *Image-based trickplay tracks*
>> For player resources optimization reasons, the use of a video track as a
>> trickplay artefact is not always possible, and a lot of player providers
>> recommend the use of image thumbnails tracks instead of special low
>> framerate video tracks. DASHIF IOP section 6.2.6 covers this use case but
>> there is equivalent support in the HLS RFC. There is the Image Media
>> playlists HLS extension proposal from Roku/Disney/WarnerMedia here
>> https://github.com/image-media-playlist/spec but its relevance/adoption
>> is currently limited by the fact that it's not part of the RFC. Same logic
>> here: even if not supported by Apple players which don't need it as they
>> can leverage I-frame tracks, it would be super useful for the rest of the
>> HLS ecosystem to get this officially part of the RFC.
>>
>>
>>
>> Thanks for your consideration,
>>
>> Nicolas
>>
>>
>>
>> ----------------
>>
>> Nicolas Weil | *Senior Product Manager – Media Services*
>>
>> *AWS Elemental*
>>
>>
>> --
>> Hls-interest mailing list
>> Hls-interest@ietf.org
>> https://www.ietf.org/mailman/listinfo/hls-interest
>>
>
>
> --
> Phil Cluff | Streaming Architect | +44 7983 406 937 | phil@mux.com
> --
> Hls-interest mailing list
> Hls-interest@ietf.org
> https://www.ietf.org/mailman/listinfo/hls-interest
>