Compressed formats - framed or unframed?

Compressed formats - framed or unframed?

[Dave Stevenson]

Hi All.

I'm trying to get a V4L2 M2M driver sorted for the Raspberry Pi to
allow access to the video codecs. Much of it is working fine.

One thing that isn't clear relates to video decode. Do the compressed
formats (eg V4L2_PIX_FMT_H264) have to be framed into one frame per
V4L2 buffer, or is providing unframed chunks of an elementary stream
permitted. The docs only say "H264 video elementary stream with start
codes.". Admittedly timestamps are nearly meaningless if you feed in
unframed data, but could potentially be interpolated.

What does other hardware support?

I could handle it either way, but there are some performance tweaks I
can do if I know the data must be framed.

Thanks in advance.
  Dave

Re: Compressed formats - framed or unframed?

[Dave Stevenson]

On 26 April 2018 at 17:25, Dave Stevenson
<dave.stevenson@raspberrypi.org> wrote:
> Hi All.
>
> I'm trying to get a V4L2 M2M driver sorted for the Raspberry Pi to
> allow access to the video codecs. Much of it is working fine.
>
> One thing that isn't clear relates to video decode. Do the compressed
> formats (eg V4L2_PIX_FMT_H264) have to be framed into one frame per
> V4L2 buffer, or is providing unframed chunks of an elementary stream
> permitted. The docs only say "H264 video elementary stream with start
> codes.". Admittedly timestamps are nearly meaningless if you feed in
> unframed data, but could potentially be interpolated.
>
> What does other hardware support?
>
> I could handle it either way, but there are some performance tweaks I
> can do if I know the data must be framed.

Does anyone have any view on this?

Thanks
  Dave