Open cconcolato opened 2 years ago
From Sep 28 Media WG teleconference (https://www.w3.org/2021/09/28-mediawg-minutes.html), we had agreement that updating the BSF to match what implementations do (not require ftyp
, and if it's syntactically correct in the stream - e.g. in the right parsing position in the grammar - skip it without checking brands or UA support for them.) With such skipping, the other references in the BSF to ftyp
's brands and their requirements should also be dropped. The same goes for styp
.
We could also assist content providers and implementors by providing a non-normative note describing this -- essentially, implementations should attempt to parse and play what they can, and that ftyp
and styp
brands' support verification has not been implemented and enforcing such verification could regress existing content playback.
The BSF spec indicates the following about the "File Type Box" (https://www.w3.org/TR/mse-byte-stream-format-isobmff/#iso-init-segments):
In my testing, none of the browsers I tested (Chrome, Firefox, Safari) care about the presence or contents of the
ftyp
box. Bullet 2. above would mean that browsers have a mapping (brand, requirements), which I don't think they have. Also 1) contradicts the design of ISOBMFF which says that you can process a file if you understand at least one brand.I think the BSF can safely be updated to match what implementations do and simply say that an Initialization Segment is a
moov
box, optionally preceded by boxes.Note that the same type of sentence exists also for the
styp
box, and could be safely removed I think.