[FFmpeg-devel] [PATCHv6 4/4] libavcodec: v4l2: add support for v4l2 mem2mem codecs

[Jorge Ramirez]

On 08/28/2017 02:16 PM, Jorge Ramirez wrote:
> On 08/28/2017 12:47 PM, wm4 wrote:
>>> I guess that instead of polling for the AVBufferRef to be unreferenced,
>>> I can associate a sync (ie a sempahore) to each buffer, take it on
>>> release and post the semaphore on the AVBufferRefs being unreferenced.
>>> that is actually pretty clean in terms of cpu usage.
>> That would just freeze an API user calling avcodec_close(), when it
>> keeps around decoded AVFrames for later use.
>
> yes I understand, but it does avoid using the CPU to poll for the 
> buffer release (an incremental improvement)
>
> but yes I think that the message is that even though this proposal 
> might suffice for simple video players (my tests) is not good enough 
> for other users requiring the decoded frame for post processing.
>
> is this a blocker to upstream or could I continue working with it 
> flagging the encoder/decoder as EXPERIMENTAL? the current situation at 
> least keeps video players happy.
>
>

just wondering, if the AVBufferRefs must live for ever (ie, after the 
codecs have been closed), what do other codecs dequeuing from a limited 
number of re-usable hardware allocated buffers do?
do they use the CPU allocate and copy the data from those buffers to the 
heap?