rtmp: proper handling of extended timestamps (take 2)

[alfredh]

draft, needs more testing...

[alfredh]

ncannasse/haxevideo#36

https://lists.mplayerhq.hu/pipermail/rtmpdump/2014-December/002406.html

[alfredh]

when type 3 is used for fragmented packets, the extended timestamp is duplicated
from the previous type 0 or type 1/2 packet. this is redundant information.
from testing with ffmpeg, it looks like this value is ignored.

when receiving a single type 3 packet (no fragmentation) the header info should
be copied from the previous type 0 or 1/2 packet. in this case the extended timestamp
should be read and used.

	case 3:
		if (!chunk->mb) {

			chunk->mb = mbuf_alloc(chunk->hdr.length);
			if (!chunk->mb)
				return ENOMEM;

			if (chunk->hdr.format == 0) {
				chunk->hdr.timestamp_delta =
					chunk->hdr.timestamp;
			}

			chunk->hdr.timestamp += chunk->hdr.timestamp_delta;
		}

		if (chunk->hdr.ext_ts) {

			uint32_t ext_ts;

			if (mbuf_get_left(mb) < 4)
				return ENODATA;

			ext_ts = ntohl(mbuf_read_u32(mb));

			if (chunk->hdr.format == 0)
				chunk->hdr.timestamp = ext_ts;
			else
				chunk->hdr.timestamp_delta = ext_ts;
		}

[alfredh]

I did some more testing with ffmpeg.

I made a hack in libre, where the extended timestamp is not added
for type 3 (this is a protocol error).

in this case ffmpeg gave lots of warnings and closed the connection:

[rtmp @ 0x7fd970d1f4c0] Too short chunk size change packet (0)
[flv @ 0x7fd97180a600] Packet mismatch 511311794 11 600366
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 2046522 != 10293543
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 8481913 != 6367078
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 3870470 != 6192111
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 10199958 != 5529381
frame=  248 fps= 24 q=28.0 size=     256kB time=00:00:10.51 bitrate= 199.4kbits/s dup=1 drop=0 speed=1.02x   [tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 9836232 != 11058686
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 16612785 != 10903604
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 14281432 != 14340103
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 8113144 != 9933097
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 6357270 != 13125711
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 10539962 != 2336863
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 4674907 != 8470418
[tcp @ 0x7fd970c0cc00] RTMP packet size mismatch 10346371 != 15941361

The ffmpeg command used was:

$ ffmpeg -y -loglevel info -listen 1 -i rtmp://127.0.0.1:1935 out.mp4