Peter Maersk-Moller wrote: > I'm in the need for suggestions for where to look for the cause of frame > drops for decoded signals from Canal Digital on 1West (CONAX). What I > experience is a typical 50-70 encoded frames missing (PTS jumps 2-2.8 > secs) every 1-20 minute. Here is my setup. > > ReceiverPCs----FastEthernet--Switch--FastEthernet----DecoderPCs > > The receiver PCs have a mix of 1-4 Hauppauge Nexus-s/Nova-s/Nova-CI-s > > The receiver PCs runs kernel 2.6.10, uses vdr 1.39 to tune into the > channels and enabling the CONAX/CAM and uses dvbstream to stream the > channels onto the switched Fast Ethernet. > > On the Decoder PCs I run my own libmpeg2 based decoder application. Here > I observe that the PTS of the decoded signal every now and then (1-20 > minutes interval) jumps 50-70 frames (2-2.8 secs) when the signal comes > from Canal Digital (CONAX Encryption). Same setup works well when the > signal is FTA from Sky. > > Inspecting the RTP packet sequence number on the Decoder PC reveal very > little or no rtp packet drops, so that is not the cause of the problem. > > So my conclusion is that either CanalDigitals signal has severe jumps in > PTS (especially for NRK1 and NRK2), or the receiver PCs builds a > lag/buffer that eventually gets dropped (50-70 decoded frames). Assuming > the latter, then where can the data get lost ? Is it on the Hauppauge > (TT) receivers or in the driver/kernel or in the dvbstream app. ? - at 4Mbit/s two seconds give you one MByte. Is there a 1MB buffer somewhere that could slowly run full and then get dropped completely to recover? (maybe the bitrate of the paytv channels is higer than for FTA?) - do and verify a recording on a receiver PC with one Nova card first - PTS discontinuities are allowed in the MPEG standard; is there actually something missing? is the discontinuity_indicator set? does the PTS jump happen only for video and not for audio? - how does your libmpeg2 based decoder app sync to the dvbstream transmitter to ensure buffers never over/underrun? Johannes
