[FFmpeg-devel] [PATCH 3/3] avcodec/cbs_vp9: discard empty fragments

[Mark Thompson]

On 30/10/18 23:45, James Almer wrote:
> On 10/30/2018 8:19 PM, Mark Thompson wrote:
>> On 30/10/18 19:21, James Almer wrote:
>>> Signed-off-by: James Almer <jamrial at gmail.com>
>>> ---
>>>  libavcodec/cbs_vp9.c | 3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> diff --git a/libavcodec/cbs_vp9.c b/libavcodec/cbs_vp9.c
>>> index 7498be4b73..812be4ddd5 100644
>>> --- a/libavcodec/cbs_vp9.c
>>> +++ b/libavcodec/cbs_vp9.c
>>> @@ -403,6 +403,9 @@ static int cbs_vp9_split_fragment(CodedBitstreamContext *ctx,
>>>      uint8_t superframe_header;
>>>      int err;
>>>  
>>> +    if (frag->data_size <= 0)
>>> +        return 0;
>>> +
>>>      // Last byte in the packet.
>>>      superframe_header = frag->data[frag->data_size - 1];
>>>  
>>>
>>
>> Seems fine, but why would an empty fragment appear here?
> 
> I noticed this when i tried to reimplement the vp9 parser using cbs_vp9.
> Libavformat passed dummy zero sized packets that resulted in cbs errors
> trying to read the frame header.

Seems like we'd prefer they didn't get this far (zero-sized packets are flush packets to decoders), but oh well.

>> (Given that H.26[45] has pretty much the same check, maybe it should be in the generic code.)
> 
> And AV1 has a while (size > 0), so yeah, it may be a good idea.

I don't mind - this patch LGTM, make it common if you like.

Thanks,

- Mark