[FFmpeg-devel] [PATCH v2 04/11] avformat/muxers: Add non-blocking mode support for av_write_trailer

[Jan Sebechlebsky]

On 08/22/2016 09:51 AM, Michael Niedermayer wrote:
> On Thu, Aug 11, 2016 at 02:38:29PM +0200, sebechlebskyjan at gmail.com wrote:
>> From: Jan Sebechlebsky <sebechlebskyjan at gmail.com>
>>
>> This makes av_write_trailer not to free the resources if write_trailer
>> call returns AVERROR(EAGAIN) allowing repeated calls of write_trailer of
>> non-blocking muxer.
>>
>> Signed-off-by: Jan Sebechlebsky <sebechlebskyjan at gmail.com>
>> ---
>>   Changes since the last version of the patch:
>>   - Added assert to the part of the code dealing with flushing
>>     interleaved packets which should not be entered if
>>     muxer in non-blocking mode is used.
>>     (also there is assert for the same condition added into
>>      av_interleaved_write_packet in one of the following
>>      patches).
>>
>>   libavformat/avformat.h |  6 +++++-
>>   libavformat/mux.c      | 10 ++++++++--
>>   2 files changed, 13 insertions(+), 3 deletions(-)
>>
>> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
>> index d8a6cf3..2cc3156 100644
>> --- a/libavformat/avformat.h
>> +++ b/libavformat/avformat.h
>> @@ -2510,8 +2510,12 @@ int av_write_uncoded_frame_query(AVFormatContext *s, int stream_index);
>>    *
>>    * May only be called after a successful call to avformat_write_header.
>>    *
>> + * If AVFMT_FLAG_NONBLOCK is set, this call may return AVERROR(EAGAIN)
>> + * meaning the operation is pending and the call should be repeated.
>> + *
>>    * @param s media file handle
>> - * @return 0 if OK, AVERROR_xxx on error
>> + * @return 0 if OK, AVERROR(EAGAIN) in case call should be repeated,
>> + *         other AVERROR on error
>>    */
>>   int av_write_trailer(AVFormatContext *s);
>>   
>> diff --git a/libavformat/mux.c b/libavformat/mux.c
>> index e9973ed..3ae924c 100644
>> --- a/libavformat/mux.c
>> +++ b/libavformat/mux.c
>> @@ -1204,11 +1204,14 @@ int av_write_trailer(AVFormatContext *s)
>>       for (;; ) {
>>           AVPacket pkt;
>>           ret = interleave_packet(s, &pkt, NULL, 1);
>> -        if (ret < 0)
>> -            goto fail;
>>           if (!ret)
>>               break;
>>   
>> +        av_assert0(!(s->flags & AVFMT_FLAG_NONBLOCK));
> this would abort on any error not just EAGAIN
I think it will abort in case interleave_packets does not return 0 from 
the first call in loop, which means that interleaving was used (because 
there are some packets to be flushed) and that situation cannot happen 
with AVFMT_FLAG_NONBLOCK set when interleaving is forbidded. The next 
patch also adds assert to av_interleaved_write_packet. But I think the 
assert here is on the right place, or have I misunderstood the problem 
you're pointing out?

Regards,
Jan