[libav-devel] [PATCH] lavc: Deprecate rtp_callback field

Martin Storsjö martin at martin.st
Fri Nov 20 11:52:16 CET 2015

On Fri, 20 Nov 2015, Andreas Cadhalpun wrote:

> On 19.11.2015 09:45, Vittorio Giovara wrote:
>> This function returns the encoded data of a frame, one slice at a time
>> directly when that slice is encoded, instead of waiting for the full
>> frame to be done. However this field has a debatable usefulness, since
>> it looks like it is just a convoluted way to get data at lowest
>> possible latency, or a somewhat hacky way to store h263 in RFC-2190
>> rtp encapsulation.
>> Moreover when multi-threading is enabled (which is by default) the order
>> of returned slices is not deterministic at all, making the use of this
>> function not reliable at all (or at the very least, more complicated
>> than it should be).
>> So, for the reasons stated above, and being used by only a single encoder
>> family (mpegvideo), this field is deemed unnecessary, overcomplicated,
>> and not really belonging to libavcodec. Libavformat features a complete
>> implementation of RFC-2190, for any other case.
>> Signed-off-by: Vittorio Giovara <vittorio.giovara at gmail.com>
>> ---
>> I received more feedback from Opal, so I mentioned their usecase in
>> the commit log. Also added APIchange entry as Andreas requested.
>> Vittorio
>>  doc/APIchanges             | 3 +++
>>  libavcodec/avcodec.h       | 6 ++++++
>>  libavcodec/mpegvideo_enc.c | 8 ++++++++
>>  libavcodec/version.h       | 5 ++++-
>>  4 files changed, 21 insertions(+), 1 deletion(-)
>> diff --git a/doc/APIchanges b/doc/APIchanges
>> index fbabb51..52b09ae 100644
>> --- a/doc/APIchanges
>> +++ b/doc/APIchanges
>> @@ -13,6 +13,9 @@ libavutil:     2015-08-28
>>  API changes, most recent first:
>> +2015-xx-xx - xxxxxxx - lavc 57.9.1 - avcodec.h
>> +  Deprecate rtp_callback in favour of AVFormat rtpenc muxer.
> Does that mean opal can use the AVFormat rtpenc muxer for its purposes?
> I'm just wondering, because you previously mentioned that there was no
> replacement.

The rtpenc muxer is not related to the rtp_callback whatsoever. The rtpenc 
muxer is not a replacement, and even if you used rtp_callback before, you 
still also would have used the rtpenc muxer (or an equivalent).

Vittorio, how many times do we have to explain this?

The rtp_callback was only a way to get one slice returned from the encoder 
at a time, without having to wait for the full frame to be encoded. You 
can't replace that with a muxer, that's just plain nonsense.

// Martin

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