Picture quality

[Enormous]

For all of those who have taken the plunge: what is the (playback) picture quality like using the Linux edition? Could anyone shed some light on this? I'm especially interested in how it compares to using the NVidia PureVideo decoders on the Windows side.

Thanks!

[laurenglenn]

Honestly, I don't seem much of a difference between this and the Windows version. Although, the Windows version of the Hauppauge driver has a Temporal Filter which blurs the video too much for my taste.

Lauren

[Insyte]

It appears to me to be cleaner than the playback on my Tivo.

[stevech]

what do you mean by "cleaner"?

[Insyte]

Less compression artifact.

[Insyte]

Originally Posted by Insyte

Less compression artifact.

Now that I've been playing with it more, I have to reverse this statement: When switching between TiVo and Sage on my AV box, it's pretty obvious that the TiVo output is sharper and cleaner.

Also, when transferring the video files to my computer and watching them with VLC, the level of compression artifact is quite disturbing. I currently have the video quality set to the "3.2GB/hr" setting, which I expected to be near-dvd quality.

My graphics card is a GeForce 4MX and the caputre card is a PVR150.

[stanger89]

Originally Posted by Insyte

Now that I've been playing with it more, I have to reverse this statement: When switching between TiVo and Sage on my AV box, it's pretty obvious that the TiVo output is sharper and cleaner.

My graphics card is a GeForce 4MX and the caputre card is a PVR150.

That explains that probably. It's pretty hard to get really great SD output from a video card due to the sub-optimal signal path (unnecessary deinterlacing and scaling).

Also, when transferring the video files to my computer and watching them with VLC, the level of compression artifact is quite disturbing. I currently have the video quality set to the "3.2GB/hr" setting, which I expected to be near-dvd quality.

What's your source like? You shouldn't be getting compression artifacts at that setting unless you've got a pretty noisy source. Maybe post a screenshot.

Also have you calibrated your capture settings?

[Insyte]

Originally Posted by stanger89

That explains that probably. It's pretty hard to get really great SD output from a video card due to the sub-optimal signal path (unnecessary deinterlacing and scaling).

What do you mean by "SD output"? And is there a better alternative to using S-Video output from a graphics card?

What's your source like?

Analog from a building-wide DirecTV system. It appears clean and sharp both through my TiVo and when connected directly to the TV. There is a single splitter sending the signal to the TiVo and the Sage box.

Maybe post a screenshot.

I'll see if I can find a representative sample tomorrow.

Also have you calibrated your capture settings?

I've played with the "color calibration" on the source settings, if that's what you mean. The image does look less washed out now that I've tweaked the brightness and contrast a bit.

-Ben

[Insyte]

Originally Posted by Insyte

What do you mean by "SD output"?

D'oh... Standard definition, I presume?

-Ben

[Wheemer]

Also the Svideo out on that video card isn't exactly perfect. I noticed a huge PQ improvement when upgrading from a Nvidia MX440 to a FX 5500.

[stevech]

DVR 101 for me...

With my tuner/encoder (Hauppauge USB2) doing mpeg compression (is this de-interleaved?), then the PC has to rasterize to fit the video card aspect ratio and pixel sizes, the the video-out chip has to resample the image and re-interlace for (e.g., NTSC), the end result on my TV is the playback quality is much reduced versus plain analog cable.

Am I correct that buying a better/different video card won't improve the quality, because of all the resampling?

Am I correct that a card like the Hauppauge '350 with a hardware decoder *will* improve the quality because the resampling from the video card's memory is *not* done (mpeg from disk goes to the hardware decoder)? But if the mpeg *encoder* deinterleaves, there's still resamping to re-interleave, but not resize, right?

[stanger89]

Originally Posted by stevech

DVR 101 for me...

With my tuner/encoder (Hauppauge USB2) doing mpeg compression (is this de-interleaved?), then the PC has to rasterize to fit the video card aspect ratio and pixel sizes, the the video-out chip has to resample the image and re-interlace for (e.g., NTSC), the end result on my TV is the playback quality is much reduced versus plain analog cable.

That's the jist, though technically it's like this:

Tuner encoder creates an Interlaced MPEG-2 stream
Upon playback, the (software) decoders will deinterlace it and render it to the video card
The video card will scale it to the desktop resolution (+/- any zoom you have set)
The "TV Encoder" in the video card will take that deinterlaced/scaled video and convert it to NTSC (or PAL) interlaced video.

Am I correct that buying a better/different video card won't improve the quality, because of all the resampling?

Probably, it's hard to say really, some cards have pretty good TV-outs, some have bad ones. It's not always clear which are which.

Am I correct that a card like the Hauppauge '350 with a hardware decoder *will* improve the quality because the resampling from the video card's memory is *not* done (mpeg from disk goes to the hardware decoder)?

Correct, basically the hardware decoder just "unzips" the video just like it was before it was encoded. (Gross simplification I know).

But if the mpeg *encoder* deinterleaves, there's still resamping to re-interleave, but not resize, right?

No resampling (which is the same thing a resizing really) and since the video is stored interlaced in the MPEG file there's no "re-interlacing".

[stevech]

thanks!

Now I wonder if the Hauppauge PVR USB2 which doesn't have MPEG hardware decoding, was a poor choice?

I've read that the '350 card has other issues - with the on-screen-display (OSD) menus going through the mpeg decoder port; or maybe the software (SageTV) causes the video-out to toggle over to a VGA buffer TV encoder for the OSD? Not sure how graphic overlays work in this case though.

[Enormous]

Is this all still on the topic of PQ in the Linux edition?