[linux-dvb] Pinnacle PCTV Sat HDTV Pro USB (452e) packet loss

Daniel Golle daniel.golle at gmail.com
Thu Dec 13 16:45:58 CET 2007


i also noticed glitches on some channels, but not all.
Using szap2 (or the patched version of VDR 1.5) on Astra 19.2E
Das
Erste:11836:hC34M2S0Z0:S19.2E:27500:101:102=deu,103=2ch;106=dd:104:0:28106:1:1101:0
works perfect and didn't show a single error in several hours of
recording, while
ORF2E:12692:hC56M2S0Z0:S19.2E:22000:170:171=deu:505:0:13014:1:1117:0
rarely gives any complete picture at all - usually vdr-softdevice
crashes after some seconds...
this pointed me to a possible dependency on the symbol rate, but i
didn't investigate it further. as I'm currently waiting for a new LNC to
be delivered, i cannot run any meaningful test at this moment (but
hopefully next week).

regards

Daniel

On Thu, 2007-12-13 at 13:20 +0100, linux-dvb-request at linuxtv.org wrote:
> Although this device is not yet officially supported, I've been trying
> to get it working following success reported by others in an earlier
> thread. I've followed the instructions in the DVB wiki entry for this
> device, and have succeeded in tuning the device using the patched
> version of szap, and recording a transport stream (using
> cat /dev/dvb/adapter0/dvr0 > recording.ts).
> 
> However, the transport stream shows up discontinuity errors which
> manifest as glitches in the playback. From the stats produced by TS
> Reader the rate of loss is typically around 1 packet in 700, though it
> varies from run to run. 
> 
> I realise the simplest explanation for this would be a poor quality
> signal. However, the device performs flawlessly under Windows XP in
> exactly the same hardware configuration (same computer, dish, and sat
> feed) when tuned to the same channels. This seems to rule out signal
> quality as a cause unless the linux driver does not configure the
> device's error correction properly. Is there any possibility this
> could be the case ?
> 
> I've also tried running the linux configuration on two different
> computers - an AMD X2 4600 with Asus M2NPV-VM mobo, and a Via EPIA5000
> system (with a PCI 5-port USB2.0 card). The same problem occurs on
> both systems.
> 
> I'm using kernel version 2.6.18-2. I also have two DVB-T USB adapters
> which work with the same software configuration with no packet loss.
> 
> The channels I've tried are BBC 1 London and BBC HD. Obviously, the
> data rate is much higher on the HD channel. I've cross-checked with
> the XP configuration to make sure that the frequencies, polarity, etc.
> are correct in the channels.conf file.
> 
> Note that during the BBC HD trial from Crystal Palace I was able to
> record this channel from a DVB-T adapter without packet loss even on
> the EPIA5000 (533 MHz Via Eden processor).
> 
> I'm unable to determine at what point in the processing chain the
> packets are being lost. I temporarily inserted some checks for
> continuity errors on a specific pid in the 'dvb_dmxdev_ts_callback'
> function in dmxdev.c. This showed packets had already gone missing at
> this point in the driver. I don't know my way around the code well
> enough to be able to pursue it further. In particular, I can't tell
> whether the packets are being discarded somewhere in the driver, or
> within the device itself. The only kind of errors which I detect are
> continuity errors. Does the device filter out all packets in error or
> does it pass them through to the driver with the appropriate error
> flags set in the packet header ?
> 
> Has anybody succeeded in getting an error free transport stream from
> this device ? If not, are there any ideas about where the problem
> might be ?
> 
> Thanks,
> John




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