[FFmpeg-devel] [PATCH] lavc/hevc: Allow arbitrarily many trailing_zero_8bits after a NAL unit in bytestream format.

[Hendrik Leppkes]

On Thu, Mar 17, 2016 at 1:21 PM, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
> On Thu, Mar 17, 2016 at 1:10 PM, Mark Thompson <sw at jkqxz.net> wrote:
>>>
>>> Wouldn't it be simpler then to add a condition to the existing loop to
>>> only error out when no NALs exist?
>>
>> I apologise if I'm not understanding exactly what you mean, but wouldn't that
>> then accept any trailing garbage at all as long as there is one valid NAL unit?
>
> Yes, it would. From what I can tell, that just how h264 works as well,
> and to share code, it could probably even be adjusted to use
> avpriv_find_start_code, since the structure of the start codes is
> exactly the same.
> Decoders should generally be rather forgiving, and if we can decode
> one or more NALs from a buffer, then we shouldn't discard all of that
> work on account of a few random bytes, IMHO.
>
> That said, how do these extra zeros even end up being left over? From
> what I can tell, ff_hevc_extract_rbsp should consume all data from the
> previous start code up to the next one?
>

Something I forgot to mention, it would already skip random garbage in
between NALs right now, and just error out when its at the end of a
buffer. That seems inconsistent, if anything.

- Hendrik