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

[Tobias Rapp]

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.

Regards, Tobias