[mythtv-users] How to improve capture quality
Jay Mallar
jaymallar at gmail.com
Mon Oct 22 19:56:37 UTC 2007
Jay Mallar wrote:
> Steve Peters - Priority Electronics wrote:
>> What is your recording bitrate set at?
>>
>> -----Original Message-----
>> *From:* mythtv-users-bounces at mythtv.org
>> [mailto:mythtv-users-bounces at mythtv.org] *On Behalf Of *Jay Mallar
>> *Sent:* Monday, October 22, 2007 9:46 AM
>> *To:* Discussion about mythtv
>> *Subject:* [mythtv-users] How to improve capture quality
>>
>> My machine:
>>
>> Intel Quad Core (Q6600)
>> Asus P5N32-Plus MB
>> EVGA GeForce 6200-LE
>> Hauppauge PVR-250
>>
>> My video card is connected to my monitor via the VGA port and to
>> my TV. The TV connection is S-video out to an RF Modulator to
>> my TV's cable input.
>>
>> The quality of video captured via the PVR-250 isn't what I'd
>> hoped for. I thought at first that the video card or the
>> connection to my TV had been the problem, but that isn't the
>> case. I've watched DVDs and AVIs on the machine via the same
>> video connection to my TV and the images are sharp and clean.
>>
>> However when I capture video and replay it, it is grainy at
>> best. When the image changes rapidly, I get what I can only hope
>> to describe as problems with refresh timing; I see this big
>> horizontal lines where it looks like the image was painted to a
>> certain point and then repainted again before it finished. It's
>> worse with high-contrast, fast action.
>>
>> I suspect I need to tweak the capture settings, but I'm curious
>> what the best values are. I tried using the settings from the
>> Wiki (http://www.mythtv.org/wiki/index.php/Recording_Parameters),
>> but those don't seem to be getting me where I'd hoped to be.
>>
>> At the very least, shouldn't I be able to get the quality I see
>> when I hook my TV directly to the satellite STB or to the output
>> from my TiVo (Are these TiVo values accurate?
>> http://alfter.us/tivo2svcd.shtml?)
>>
>> Setting the resolution to anything higher than width of 480 seems
>> to have no effect. Myth won't let me change height above 480.
>> I got a bit lost the settings for bitrate etc.. Not sure if
>> bitrate is avg or min or both, and not sure if Myth uses VBR or
>> CBR. From what I've read avg bitrate should be set below max
>> bitrate, but I'm not getting good results trying to tweak on my own.
>>
>> ------------------------------------------------------------------------
>>
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>> mythtv-users at mythtv.org
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>>
> Right now It's set to 480x480, MPEG-2 PS, 4:3, BR 5800, MBR 8000, but
> I've also used the defaults of 480x480, MPEG-2 PS, 4:3, BR 4500, MBR
> 6000 as well and honestly can't tell the difference between them.
>
Here's some examples of the quality problems I'm having.
I recorded these by doing "cat /dev/video0 > file".
mysample.mpg
Notice at the beginning and end of the sample when the guys arms are
flailing against the snow. Notice the horizontal lines/blocks that are
showing up.
mysample-2.mpg
When the guy is shaking the girl, notice how pixelated his jacket is.
This sample really highlights the poor quality/grainiess.
Any ideas oh now to improve it?
Also - when I run "mplayer /dev/video0" it dumps out some useful stuff:
:mplayer /dev/video0
MPlayer 1.0rc2-4.1.2 (C) 2000-2007 MPlayer Team
CPU: Intel(R) Core(TM)2 Quad CPU @ 2.40GHz (Family: 6, Model:
15, Stepping: 7)
CPUflags: MMX: 1 MMX2: 1 3DNow: 0 3DNow2: 0 SSE: 1 SSE2: 1
Compiled with runtime CPU detection.
Playing /dev/video0.
MPEG-PS file format detected.
VIDEO: MPEG2 720x480 (aspect 2) 29.970 fps 9800.0 kbps (1225.0 kbyte/s)
==========================================================================
Opening video decoder: [mpegpes] MPEG 1/2 Video passthrough
VDec: vo config request - 720 x 480 (preferred colorspace: Mpeg PES)
Could not find matching colorspace - retrying with -vf scale...
Opening video filter: [scale]
The selected video_out device is incompatible with this codec.
Try appending the scale filter to your filter list,
e.g. -vf spp,scale instead of -vf spp.
VDecoder init failed :(
Opening video decoder: [libmpeg2] MPEG 1/2 Video decoder libmpeg2-v0.4.0b
Selected video codec: [mpeg12] vfm: libmpeg2 (MPEG-1 or 2 (libmpeg2))
==========================================================================
==========================================================================
Opening audio decoder: [mp3lib] MPEG layer-2, layer-3
AUDIO: 48000 Hz, 2 ch, s16le, 256.0 kbit/16.67% (ratio: 32000->192000)
Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3)
==========================================================================
AO: [alsa] 48000Hz 2ch s16le (2 bytes per sample)
Starting playback...
VDec: vo config request - 720 x 480 (preferred colorspace: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 1.33:1 - prescaling to correct movie aspect.
VO: [x11] 720x480 => 720x540 Planar YV12
[swscaler @ 0x87aaa70]SwScaler: using unscaled yuv420p -> bgr565 special
converter
A: 5.7 V: 6.3 A-V: -0.679 ct: -0.454 137/137 3% 5% 1.1% 0 0
Exiting... (Quit)
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