[FFmpeg-devel] [RFC] rtpdec: Reordering RTP packets

[Michael Niedermayer]

On Wed, May 26, 2010 at 12:19:55AM +0300, Martin Storsj? wrote:
> On Tue, 25 May 2010, Michael Niedermayer wrote:
> 
> > very low delay is absolutely mandatory for some applications and refusing
> > to return the correct packet if you have 2 packets is just insane.
> 
> Well, that's what the code currently does, too.
> 
> The code we've proposed up til now doesn't make the "minimum delay" case 
> any different from what it does now, if the reordering is disabled.
> 
> > i dont object to a max_delay (in milli second or such)
> > i object to the code returning the wrong packet of several
> > that it has immedeately available if max_delay=0 or for example
> > if there are 5 packets in the kernel buffer and max_delay=1 to then
> > limit reordering to 1 packet (and drop 3 as they kernel buffer overflows
> > till the next call of av_read_frame())
> 
> I tried implementing something like the thing I outlined above, and this 
> should handle these cases where all the necessary packets are in kernel 
> buffers but in incorrect orders.
> 
> That is, first we try to receive as many packets as we need to get the 
> correct one using nonblocking reads. If the correct one isn't available at 
> all, then we return the first one of the packets in the reorder queues 
> when max_delay has expired.
> 
> The attached patches does this - they're untested, but try to show roughly 
> how this could be implemented.
[...]
> @@ -1806,9 +1807,27 @@ static int rtsp_fetch_packet(AVFormatContext *s, AVPacket *pkt)
>  #endif
>      case RTSP_LOWER_TRANSPORT_UDP:
>      case RTSP_LOWER_TRANSPORT_UDP_MULTICAST:
> -        len = udp_read_packet(s, &rtsp_st, buf, sizeof(buf), 1);
> +        len = udp_read_packet(s, &rtsp_st, buf, sizeof(buf), wait);
>          if (len >=0 && rtsp_st->transport_priv && rt->transport == RTSP_TRANSPORT_RTP)
>              rtp_check_and_send_back_rr(rtsp_st->transport_priv, len);
> +        if (len == FF_NETERROR(ETIMEDOUT) && !wait) {
> +            /* No more queued packets in the kernel buffers */
> +            if (rt->transport == RTSP_TRANSPORT_RTP && s->max_delay <= 0) {
> +                /* max_delay expired, try to flush one of the queued packets,

s->max_delay <= 0 and max_delay expired dont sound like they match
or are you intending to decrease s->max_delay ?




[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Opposition brings concord. Out of discord comes the fairest harmony.
-- Heraclitus
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