[FFmpeg-devel] [PATCH v2] avcodec/av1dec: convert to receive_frame()

[James Almer]

On 5/20/2023 2:17 PM, Andreas Rheinhardt wrote:
> James Almer:
>> On 5/20/2023 2:07 PM, Andreas Rheinhardt wrote:
>>> James Almer:
>>>> On 5/20/2023 1:59 PM, Andreas Rheinhardt wrote:
>>>>> James Almer:
>>>>>> On 5/20/2023 1:12 PM, Anton Khirnov wrote:
>>>>>>> Quoting James Almer (2023-05-20 03:50:57)
>>>>>>>> Signed-off-by: James Almer <jamrial at gmail.com>
>>>>>>>> ---
>>>>>>>>      libavcodec/av1dec.c | 75
>>>>>>>> +++++++++++++++++++++++++++++++++------------
>>>>>>>>      libavcodec/av1dec.h |  4 +++
>>>>>>>>      2 files changed, 60 insertions(+), 19 deletions(-)
>>>>>>>
>>>>>>> The patch makes the code longer and introduces an evil backward goto.
>>>>>>> So some comment on why is this an improvement would be appropriate.
>>>>>>
>>>>>> It's an improvement because it removes the auto-inserted
>>>>>> av1_frame_split
>>>>>> from the process, making the decoder handle temporal units with more
>>>>>> than one frame in them on its own. I can add that to the commit
>>>>>> message.
>>>>>>
>>>>>> The extra code is inevitable because it's the decoder who now needs to
>>>>>> fetch the packet instead of the generic code in decode.c
>>>>>
>>>>> 1. Where is the improvement in that? What is so bad about using a
>>>>> BSF to
>>>>> preprocess packets in this way?
>>>>
>>>> Much less overhead? One less instance of CBS, less function calls, less
>>>> packet references generated and moved around, etc.
>>>>
>>>
>>> This is AV1, not annex B H.2645.
>>
>> I'm sorry, i don't understand what you're trying to say. The
>> av1_frame_split bsf will split a TU into individual frames, and uses the
>> CBS framework for this. It's an unnecessary overhead when the decoder
>> can be made to handle this on its own by making it use the proper decode
>> callback.
> 
> I meant to say: Parsing AV1 is easy and fast, in contrast to H.2645 (in
> particular, annex B H.2645).

Sure, but it's still an unnecessary overhead. Right now, the parser 
spawns a CBS instance, and the decoder two. I'm removing the one that's 
superfluous.