[FFmpeg-devel] [PATCH] mpegts: Return AVERROR(EAGAIN) instead of -1 if there isn't enough data

[Martin Storsjö]

On Wed, 13 Oct 2010, Reimar D?ffinger wrote:

> On Wed, Oct 13, 2010 at 11:52:39AM +0300, Martin Storsjo wrote:
> > This makes the rtpdec queue code able to process packets more efficiently,
> > keeping the queue shorter, by parsing the next packet instead of returning
> > the unidentified error code -1 as an error.
> > ---
> >  libavformat/mpegts.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> > index d2f9f1e..13a9908 100644
> > --- a/libavformat/mpegts.c
> > +++ b/libavformat/mpegts.c
> > @@ -1742,7 +1742,7 @@ int ff_mpegts_parse_packet(MpegTSContext *ts, AVPacket *pkt,
> >          if (ts->stop_parse>0)
> >              break;
> >          if (len < TS_PACKET_SIZE)
> > -            return -1;
> > +            return AVERROR(EAGAIN);
> >          if (buf[0] != 0x47) {
> >              buf++;
> >              len--;
> 
> I'm not sure that matches the semantics of EAGAIN.
> I'd assume EAGAIN to mean "please try the exact
> same thing again until it succeeds", whereas
> here it would mean "give me more data"?
> Maybe that's okay because only one meaning is
> certain to make sense in this case, but
> I guess it should at least be documented.

Yes, I've also noticed this slight deviation from the original meaning of 
EAGAIN, but I'm not aware of any other error code that would be better fit 
for this purpose. We already use this error code consistently within the 
rtpdec code for this purpose. (Which of course doesn't mean it shouldn't 
be changed to something else, if we realize there's a better error code 
for this.)

// Martin