[FFmpeg-devel] [PATCH 2/2] examples/decode_filter_video: Add loop for draining the filtergraph

[Tobias Rapp]

On 27/03/2024 14:04, Tobias Rapp wrote:

> On 27/03/2024 13:53, Anton Khirnov wrote:
>
>> Quoting Tobias Rapp (2024-03-27 13:46:40)
>>> On 27/03/2024 13:06, Stefano Sabatini wrote:
>>>
>>>> On date Wednesday 2024-03-27 11:51:31 +0100, Tobias Rapp wrote:
>>>>> Depending on the filters used the filtergraph can produce trailing 
>>>>> data
>>>>> after feeding it the last input frame. Update the example to 
>>>>> include the
>>>>> necessary loop for draining the filtergrap.
>>>>>
>>>>> Signed-off-by: Tobias Rapp <t.rapp at noa-archive.com>
>>>>> ---
>>>>>    doc/examples/decode_filter_video.c | 19 +++++++++++++++++++
>>>>>    1 file changed, 19 insertions(+)
>>>>>
>>>>> diff --git a/doc/examples/decode_filter_video.c 
>>>>> b/doc/examples/decode_filter_video.c
>>>>> index 454c192..a57e6df 100644
>>>>> --- a/doc/examples/decode_filter_video.c
>>>>> +++ b/doc/examples/decode_filter_video.c
>>>>> @@ -276,6 +276,25 @@ int main(int argc, char **argv)
>>>>>            }
>>>>>            av_packet_unref(packet);
>>>>>        }
>>>>> +    if (ret == AVERROR_EOF) {
>>>>> +        /* signal EOF to the filtergraph */
>>>>> +        if (av_buffersrc_add_frame_flags(buffersrc_ctx, NULL, 0) 
>>>>> < 0) {
>>>>> +            av_log(NULL, AV_LOG_ERROR, "Error while closing the 
>>>>> filtergraph\n");
>>>>> +            goto end;
>>>>> +        }
>>>>> +
>>>>> +        /* pull remaining frames from the filtergraph */
>>>>> +        while (1) {
>>>>> +            ret = av_buffersink_get_frame(buffersink_ctx, 
>>>>> filt_frame);
>>>>> +            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
>>>>> +                break;
>>>> how are we supposed to handle the EAGAIN case? Shouldn't this be a
>>>> sleep and retry?
>>> Good suggestion. I could add something like usleep(100) upon EAGAIN.
>> No, EAGAIN from a filter after EOF on all inputs is a bug.
>
> Ok. Also from a second look at the example all the other locations 
> where EAGAIN is handled do not perform a retry. So adding that would 
> be orthogonal to this patch, IMHO.
>
Applied both patches. Thanks for the feedback!

Regards, Tobias