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dtvstream with HD-3000
PostPosted: Sat Nov 20, 2004 10:59 pm Reply with quote
mspice
 
Joined: 03 Nov 2004
Posts: 36




If you have a HD-3000, please download dtvstream and run it and post your experience here. It is just dtvstream -c channel_no.

Can you please post your experiences with the HD-3000 and dtvstream here? As seen in another thread, I'm getting the following error:

Code:
Lost sync at input offset 3465216
Achieved sync after 752 bytes.


I have 90%+ signal and a nice directional antenna. I can play the movies but there are some small problems (a/v sync, mencoder complans of duplicate frames, and thsi error). I know that at least one other user has mentioned the same thing.

Michael


Last edited by mspice on Sun Nov 21, 2004 12:23 pm; edited 1 time in total
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0's in .ts file
PostPosted: Sat Nov 20, 2004 11:23 pm Reply with quote
mspice
 
Joined: 03 Nov 2004
Posts: 36




I spoke with the developer of dtvstream (he generously is trying to help me with this) and he discovered something interesting. I sent him one of my .ts files from getatsc and he noticed something strange. There are groups of 752 bytes of 0's. This equates to 4 packets. He doesn't know if they are inserted inbetween data or over where data should be. This might indicate a drivr or hardware problem.

Additionally, they spacing of the errors seems to be 96256 bytes (or exactly 512 packets). It looses sync every 512 packets.

If I am understanding this correctly, then it is getting 512 of packets then getting 4 packets of all 0's. When it gets to the 0's, dtvstream complains of loosing sync, then gets sync again after the 0's end and the data comes back.

pdicamillo and I found something even more intersting. I looked at the driver code and found this line:
Code:
cx88-atsc.c:#define BUF_DEFAULT 188*512

Each packet is 188 bytes long. It looks like the card has a buffer of 512 packets. For some reason it is reading the 512 packets but it is getting 516 with an extra 4 packets of 0's. Does this mean that it is a driver or hardware problem?
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PostPosted: Sun Nov 21, 2004 12:21 am Reply with quote
pfile
 
Joined: 06 Aug 2004
Posts: 80




hmm. i wonder if this is corner case where if you read too agressively from the driver (that is, underrun the kernel buffer for the card) that you get 4 packets of 0s. the interesting thing about the number 4 is that it seems to be the unit of DMA between the driver and the card. that doesnt seem terribly relevant though, since the card pushes data to the driver via interrupts, rather than the driver pulling data from the card.

i only wonder about reading too agressively because i have never seen this problem with myth, and if anything, myth can't keep up with the stream, which seems to be the source of my problems with buffer overruns.

one thing that i have been trying tonight is to increase the size of the kernel buffer for the driver, in an attempt to solve the buffer overrun problem. something goes very wrong though, as the recordings are completely corrupted if i do this (i tried 768 packets and 1024 packets). i havent looked at the bytes coming out of the driver to see if there is a pattern to it though.

edit: man, something in that driver is hardcoded to expect a buffer size of 188*512, but i havent been able to figure out what yet. if i try 188*64 the machine eventually hangs (same with 188*256). also what's strange is that the buffer and the code store for the DMA engine are created every time recording is started, rather than once at initialization time.
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PostPosted: Sun Nov 21, 2004 11:33 am Reply with quote
Guest
 




ok, i tried dtvsream.

i am getting the same errors on the console:

Lost sync at input offset 880357376
Achieved sync after 752 bytes.
Lost sync at input offset 880453632
Achieved sync after 752 bytes.
Lost sync at input offset 880549888
Achieved sync after 752 bytes.


however, in the output data i do not see any runs of 0s. xine played the file back okay, no dropouts or anything. mplayer would not play it. then xine messed up Xv and i dont get any video anymore, but i'm sure if i restart X i'll be able to watch the video.

whats cool is that i dont get any buffer overruns even while stressing the disks with a large file copy. so i think that the buffer overruns arent really the fault of the driver, but of myth's read thread just not being able to cope with the i/o load.
run of 0's
PostPosted: Sun Nov 21, 2004 12:20 pm Reply with quote
mspice
 
Joined: 03 Nov 2004
Posts: 36




The run of 0's is in the .ts file captured from getatsc. The 0's correspond to the placement in this input stream. If you are using dtvstream to make the .m2t files then it is extracting it and throughing away the 0's.

I am with you in that I can still play the videos. I have small isues with the playing which I am hoping that resolving this will fix (a/v sync, very slightly choppy video during lots of motion, etc).
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PostPosted: Sun Nov 21, 2004 12:34 pm Reply with quote
pfile
 
Joined: 06 Aug 2004
Posts: 80




ah ha. i didnt read carefully enough. i'll try getatsc to see if i also get the 0s.

i dont understand why mplayer didnt like the file.

edit: i'm getting long runs of ffff in my output from getatsc... but no 0s.
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dtvstream with HD-3000
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