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MythTV image quality
Posted: Thu Feb 26, 2009 2:28 pm
by DaveQB
I posted this over at MythTV talk but no answers to my problem that fixed it unfortunately. Thought I would test the MythTV users here on this one.
Can anyone recognise this kind of picture distortion and what could be the cause ?
It must be in my capturing (PVR-350) as is shows this way on the big TV and also on my Desktops 19" LCD.
Just hoping someone might know instantly what could be the cause.
http://dward.name/~david/images/MythTV-PVR-350.png
Re: MythTV image quality
Posted: Thu Feb 26, 2009 10:10 pm
by hellonorman
It looks like a deinterlacing problem to me. Which could be good news if the fix is to simply turn on deinterlacing in your playback software.
Re: MythTV image quality
Posted: Thu Feb 26, 2009 10:28 pm
by DaveQB
Yeah see, I had that mentioned in MythTvtalk and tried turning deint on and off and different types etc.
I will play with it again. This happens on the backends own frontend and my Desktop running as a front end and playing back recorded shows are the same too, so its definitely in the recording, not playback.
Is there deint settings for recording ? I am not sure what deint settings I was playing with
Re: MythTV image quality
Posted: Thu Feb 26, 2009 11:06 pm
by hellonorman
Any frontend will probably have the same playback settings so just because it does the same thing on both doesn't mean the recording is bad.
My suggestion would be to try playing the file in xine outside of mythtv and enable deinterlacing. See if that cleans up the picture.
Another way to say it would be yes the recording is interlaced, so in that sense it's in the recording. But at this point the playback is the primary suspect for the ghosting and weave/teeth effect you are seeing.
Re: MythTV image quality
Posted: Thu Feb 26, 2009 11:20 pm
by DaveQB
Great thinking.
I have dumped streams with nuvexport, to, what it says is nuv's native format, but its actually and mpeg2 stream.
These playback with the same distortion. Must be in the recording, right ?
I'll have a poke around looking for recording settings. Are these different to viewing ? I mean what you see is what is recorded [especially with livetv recording]
I think I need to do some reading/googling...
Thanks
Re: MythTV image quality
Posted: Thu Feb 26, 2009 11:27 pm
by hellonorman
DaveQB wrote:
These playback with the same distortion. Must be in the recording, right ?
I'll have a poke around looking for recording settings. Are these different to viewing ? I mean what you see is what is recorded
When it comes to interlace/de-interlace no that's not neccisarily the case.
If your playback software is not taking the interlaced recording and deinterlacing properly than it will look bad even though there is nothing wrong with the recording.
I would suggest exiting myth and navigating to the actual file and playing it with xine. Turn on deinterlacing in the xine settings and see if it plays back properly.
I'm not trying to say there is no chance that your recordings have a problem. However its far more likely that it's simply not being deinterlaced properly and I don't think you have eliminated playback as the problem so far.
Re: MythTV image quality
Posted: Fri Feb 27, 2009 12:54 am
by DaveQB
Will try that, but doesn't using nuvexport remove this concern ? I mean nuvexporting to an NFS share on another PC and playing it with smplayer or xine let me see what the recording itself contains ?
I'll play around with it on the weekend some more....
Re: MythTV image quality
Posted: Fri Feb 27, 2009 1:15 am
by hellonorman
DaveQB wrote:Will try that, but doesn't using nuvexport remove this concern ? I mean nuvexporting to an NFS share on another PC and playing it with smplayer or xine let me see what the recording itself contains ?
I'll play around with it on the weekend some more....
I haven't used myth in a while so I'm not sure exactly what nuvexport does. My suggestion to play the original file is simply to keep that variable out. My guess is that nuvexport does not remove the interlacing so you are going to see the same results if your playback software doesn't deinterlace it properly.
It sounds like you may not fully understand how interlacing/deinterlacing works so you may want to research it a bit. But again my suggestion is that you need to fully explore the playback issue because it is the most likely problem.
Good Luck
Re: MythTV image quality
Posted: Fri Feb 27, 2009 2:29 am
by DaveQB
Well nuvexport dumps the stream out into mpeg2, as it was captured. Just puts together the different streams to make the recording rather just chunks like it is on the disk.
I tried playing the raw stream, like you said and same result as an nuvexport.
http://dward.name/~david/images/MythTV- ... rlaced.png
http://dward.name/~david/images/MythTV- ... rlaced.png
Played it back in xine and even tried deinterlacing it.
Deint just moved the slantly lines from top right to lower left to top left to lower right. Well that's how it looks to it.
Yes, aware of how deinterlacing works.
Maybe my card has some how been set for NTSC capture [480 lines] yet with my software trying to get PAL [576 lines] out of it.
Thanks
Re: MythTV image quality
Posted: Fri Feb 27, 2009 3:30 am
by hellonorman
DaveQB wrote:Well nuvexport dumps the stream out into mpeg2, as it was captured. Just puts together the different streams to make the recording rather just chunks like it is on the disk.
I guess I don't see the distinction here. Doesn't the cards encoder produce mpeg2 streams already? The hauppauge cards generally produce mpeg2 video with mpa audio into an mpeg2 file.
Maybe my card has some how been set for NTSC capture [480 lines] yet with my software trying to get PAL [576 lines] out of it.
That's a possibility. Did you set the playback for NTSC to test this?
If it's a PAL/NTSC issue than you of course need to set the ivtv drivers correctly. If not then I think you need to try some different deinterlace filters.
Re: MythTV image quality
Posted: Fri Feb 27, 2009 1:12 pm
by mikeh
Your not running your desktop at a low bit depth are you? It almost looks like a combination of dithering because of a low bit depth display screen, combined with the normal interlacing. I always do a deinterlace when I transcode my OTA MPEG2 captures into xvid files (with ffmpeg).
I don't know anything about your capture card, but if it isn't your displays depth is there a chance the card is set to capture to a lower bit depth?
If not maybe you could take one of your recordings and cut it to a few seconds so we can download and look at it.
Re: MythTV image quality
Posted: Mon Mar 23, 2009 2:24 pm
by DaveQB
http://storage.dward.us/videos/sample.mpg
There is a short sample of what I am getting.
I have put the said capture card [Hauppauge PVR-350] into my desktop. I am finding I can not even test it on their.
cat /dev/video0 provides a dud file.
Code: Select all
david@david /capture/TV $
ls /dev/video*
/dev/video0 /dev/video16 /dev/video24 /dev/video32 /dev/video48
Code: Select all
david@david /capture/TV $
grep ivtv /var/log/messages
Mar 23 07:26:05 david kernel: [ 35.801893] ivtv: Start initialization, version 1.1.0
Mar 23 07:26:05 david kernel: [ 35.801977] ivtv0: Initializing card #0
Mar 23 07:26:05 david kernel: [ 35.801980] ivtv0: Autodetected Hauppauge card (cx23415 based)
Mar 23 07:26:05 david kernel: [ 35.863880] ivtv0: Autodetected Hauppauge WinTV PVR-350
Mar 23 07:26:05 david kernel: [ 35.925140] tuner 2-0043: chip found @ 0x86 (ivtv i2c driver #0)
Mar 23 07:26:05 david kernel: [ 35.928902] tuner 2-0061: chip found @ 0xc2 (ivtv i2c driver #0)
Mar 23 07:26:05 david kernel: [ 35.992244] saa7115 2-0021: saa7115 found (1f7115d0e100000) @ 0x42 (ivtv i2c driver #0)
Mar 23 07:26:05 david kernel: [ 36.165540] saa7127 2-0044: saa7129 found @ 0x88 (ivtv i2c driver #0)
Mar 23 07:26:05 david kernel: [ 36.183244] msp3400 2-0040: MSP4418G-B3 found @ 0x80 (ivtv i2c driver #0)
Mar 23 07:26:05 david kernel: [ 36.193369] ivtv0: Registered device video0 for encoder MPG (4096 kB)
Mar 23 07:26:05 david kernel: [ 36.193380] ivtv0: Registered device video32 for encoder YUV (2048 kB)
Mar 23 07:26:05 david kernel: [ 36.193393] ivtv0: Registered device vbi0 for encoder VBI (1024 kB)
Mar 23 07:26:05 david kernel: [ 36.193404] ivtv0: Registered device video24 for encoder PCM (320 kB)
Mar 23 07:26:05 david kernel: [ 36.193415] ivtv0: Registered device radio0 for encoder radio
Mar 23 07:26:05 david kernel: [ 36.193429] ivtv0: Registered device video16 for decoder MPG (1024 kB)
Mar 23 07:26:05 david kernel: [ 36.193441] ivtv0: Registered device vbi8 for decoder VBI (64 kB)
Mar 23 07:26:05 david kernel: [ 36.193452] ivtv0: Registered device vbi16 for decoder VOUT
Mar 23 07:26:05 david kernel: [ 36.193462] ivtv0: Registered device video48 for decoder YUV (1024 kB)
Mar 23 07:26:05 david kernel: [ 36.193464] ivtv0: Initialized card #0: Hauppauge WinTV PVR-350
Mar 23 07:26:05 david kernel: [ 36.193482] ivtv: End initialization
Mar 23 07:26:23 david kernel: [ 79.445164] ivtv0: Loaded v4l-cx2341x-enc.fw firmware (376836 bytes)
Mar 23 07:26:23 david kernel: [ 79.507574] ivtv0: Loaded v4l-cx2341x-dec.fw firmware (262144 bytes)
Mar 23 07:26:23 david kernel: [ 79.707888] ivtv0: Encoder revision: 0x02060039
Mar 23 07:26:23 david kernel: [ 79.708036] ivtv0: Decoder revision: 0x02020023
Mar 23 07:26:23 david kernel: [ 79.896779] ivtv0: Loaded v4l-cx2341x-init.mpg firmware (155648 bytes)
I might start a new thread on this.
