[FFmpeg-devel] UDP Timeout

[Michael Niedermayer]

On Sun, Jun 05, 2011 at 03:01:26PM +0100, JULIAN GARDNER wrote:
> 
> 
> 
> 
> ----- Original Message -----
> > From: Michael Niedermayer <michaelni at gmx.at>
> > To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> > Cc: 
> > Sent: Saturday, 4 June 2011, 15:48
> > Subject: Re: [FFmpeg-devel] UDP Timeout
> > 
> > On Sat, Jun 04, 2011 at 04:41:55PM +0200, Michael Niedermayer wrote:
> >>  On Sat, Jun 04, 2011 at 02:07:14PM +0100, JULIAN GARDNER wrote:
> >>  > 
> >>  > 
> >>  > 
> >>  > >________________________________
> >>  > >From: Michael Niedermayer <michaelni at gmx.at>
> >>  > >To: FFmpeg development discussions and patches 
> > <ffmpeg-devel at ffmpeg.org>
> >>  > >Sent: Friday, 3 June 2011, 15:10
> >>  > >Subject: Re: [FFmpeg-devel] UDP Timeout
> >>  > >
> >>  > >On Fri, Jun 03, 2011 at 09:51:48AM +0100, JULIAN GARDNER wrote:
> >>  > >> Seeing a small problem in that if you have a UDP stream that 
> > stops running, we dont get a timeout from either ffmpeg or ffplay, i tracked 
> > this down to udp.c, not sure if it was my version or the modified verision.
> >>  > >> 
> >>  > >> Small mod here to return back if the return from select is an 
> > error or a timeout, my current version ran for 86mins, with modification, 20 
> > seconds
> >>  > >
> >>  > >thats strange, the code looks like it would timeout after 1 second
> >>  > >(tv.tv_sec = 1;) with your modification
> >>  > >?
> >>  [...]
> >>  > whilst your right about the 1 second timeout you will see if you look 
> > the code that the only way to leave the while loop is for an error or data to 
> > arrive.
> >>  > 
> >>  > The check <0 is only for errors, when no data is available we get a 
> > return of 0 as you said after 1 second.
> >>  > 
> >>  > Please check again.
> >> 
> >>  i know, we misunderstand each other
> >>  1 second is too short for a timeout that results after your patch
> >>  i understand it doesnt timeout before your patch
> >> 
> >>  also maybe ff_network_wait_fd() should not be run after the select
> >>  loop
> > 
> > also the AVIO_FLAG_NONBLOCK flag should be used to select behavior
> > 
> > [...]
> > 
> > -- 
> > Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> > 
> > In fact, the RIAA has been known to suggest that students drop out
> > of college or go to community college in order to be able to afford
> > settlements. -- The RIAA
> > 
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> OK ive changed the code to use the ff_network_wait_fd, and added a timeout counter, mainly for the reason that is we have no data coming in ffmpeg just waits forever
> 
> joolz
>  udp.c |   35 ++++++++++++++++++++---------------
>  1 file changed, 20 insertions(+), 15 deletions(-)
> 5b6a5d0eb9afda998d3fcb0b3f7e98e021a2755d  udp.diff
> diff --git a/libavformat/udp.c b/libavformat/udp.c
> index 7c18fb7..e56816e 100644
> --- a/libavformat/udp.c
> +++ b/libavformat/udp.c
> @@ -536,38 +536,43 @@ static int udp_read(URLContext *h, uint8_t *buf, int size)
>      UDPContext *s = h->priv_data;
>      int ret;
>      int avail;
> -    fd_set rfds;
> -    struct timeval tv;
>  
> +    ret = 0;
>      if (s->fifo) {
> +        int timeout = 10;
>  
>          do {
>              avail = av_fifo_size(s->fifo);
> +            av_log( NULL, AV_LOG_INFO, "Udp data available %d\n", avail);
>              if (avail) { // >=size) {
>  
> +                timeout = 10;
>                  // Maximum amount available
>                  size = FFMIN( avail, size);
>                  av_fifo_generic_read(s->fifo, buf, size, NULL);
>                  return size;

timeout is never read here, so setting it to 10 is unneeded


>              }
>              else {
> +                if (!(h->flags & AVIO_FLAG_NONBLOCK)) {
> +                    ret = ff_network_wait_fd(s->udp_fd, 0);
> +                    if (ret < 0)
> +                        return ff_neterrno();
> +                }
> +                else {
> +                    return 0;

i suspect that should be AVERROR(EAGAIN)


> +                }
>              }
> +        } while( --timeout);

i dont see how this timeout can reach 0
please correct me if iam wrong but this can only be reached when
data is available for 10 seconds time and at the same time
the 2nd thread reads none of it

[... ]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In fact, the RIAA has been known to suggest that students drop out
of college or go to community college in order to be able to afford
settlements. -- The RIAA
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