Picture quality from HTPCs in general

[allanp81]

I noticed while watching Wimbledon coverage on BBC HD that the frame rate looked terrible compared to my TVs internal freeview tuner. Using coreavc codec to view this channel and everything else it looks fine with.

[gxtracker]

Originally Posted by robyf

Didn't know ffdshow was capable of hardware deinterlacing. So did you set ffdshow as mpeg2 renderer or did you use some other codec and ffdshow deinterlacing as post-processing filter?

Well technically it isnt, and that is my fault for giving that impression.

Set FFDshow as your output renderer - for whatever you want. I set it for my mpeg2 and h264 renderer and dont even bother installing the MPA/MPV codec with the installation of MP.

then, in the video decoder configuration under the output setting, there is a check box labeled "Set interlaced flag in output media type" which was formerly labeled as Hardware deinterlacing. Give the tooltip a read as well - what it does is set the interlaced flag on the video when its being output. then the actual video renderer (in MP's case, the VMR) will see that its interlaced video and apply the deinterlacing video settings you have set under the video filter settings in the MP configuration. If your card supports VMR deinterlacing in hardware, then it will be done in hardware. It's a very powerful feature, unfortunately its buried under so many other options that the average user would never know this.

Originally Posted by KevL

I have used FFDShow as a post processor in the past. I used it to do some picture enhancement (denoise and sharpen). I know it can also be used as a scaler and deinterlacer and an MPeg decoder. I didn't realise it could be made to use the graphics card as a hardware accelerator. I thought it was a software filter.

All of my source material is interlaced. I think I'm right in saying that almost all video formats are interlaced.

Im sure a lot of people think like you Kev, but ffdshow is much more than a post-processor. I've found it so powerful that when I do a HTPC install, its the only thing that gets installed after the OS, and before MP.

I dont know much about television outside of North America, but over here much of our content is not interlaced video. TV shows, movies, and other pre-scripted content are displayed as progressive content. about the only thing still broadcasted as interlaced are sports, news shows, and live recorded content.

[bigj]

KevL - set bilinear filter - else your scaling will be point-sampled => very ugly.

[Taipan]

Originally Posted by gxtracker

what it does is set the interlaced flag on the video when its being output. then the actual video renderer (in MP's case, the VMR) will see that its interlaced video and apply the deinterlacing video settings you have set under the video filter settings in the MP configuration. If your card supports VMR deinterlacing in hardware, then it will be done in hardware.

What happens if some of the video is interlaced and some is progressive - does ffdshow only apply the "interlaced flag" for interlaced video and leave progressive video alone?

We have a TV channel that broadcasts in 576i and 576p and another that broadcasts in 720p. Would ffdshow handle these OK?

[myriad]

Many of the 'stuttering video' problems you are experiencing are definitely related to interlace issues. True HD TV's or monitors that support 'P' resolutions are progressive scan devices that work best with non-interlaced content. Using a good quality video card that has hardware based de-interlacing support will many times fix the stuttering problem. Just as certain playback software like VLC set to 'BOB' will often work just as well as the hardware method.

It is a shame that many broadcasters are choosing the inferior 1080i format as opposed to the 720p one. Even though 1080i 'sounds' better than 720p due to the larger number of lines of resolution it offers, in actual fact it causes no end of problems when you play it back on progressive scan TV's. PBS is one of the few US broadcasters who have chosen 720p as their broadcast format and anyone who has an over the air HD antenna will attest to the fact that PBS's quality is superior to a 1080i hockey game broadcast on CBS for example.

Speaking personally, even after 23 years in the post production industry I still come across many 'experts' from the broadcasting environment who are surprisingly ignorant about the HD formats. But the way things stand now, it is extremely unlikely that we will see TV stations broadcasting in 1080P as the bandwidth requirements are too great. Though I could show you a 1080P and a 720P signal back to back, and in a blind test you would have a 50/50 chance of identifying which was which.

Rick

[gxtracker]

Originally Posted by Taipan

What happens if some of the video is interlaced and some is progressive - does ffdshow only apply the "interlaced flag" for interlaced video and leave progressive video alone?

I believe FFDshow sets the interlaced flag for all content, regardless of whether or not the source video is interlaced content or not.

Realisticly, it shouldn't compromise picture quality at all, since on a progressive image, there is no alternate field to de-interlace.

I have no problems playing progressive or interlaced content with the option set.

Originally Posted by myriad

It is a shame that many broadcasters are choosing the inferior 1080i format as opposed to the 720p one. Even though 1080i 'sounds' better than 720p due to the larger number of lines of resolution it offers, in actual fact it causes no end of problems when you play it back on progressive scan TV's.

While I agree that it causes a huge headache for progressive scan outputing devices, Interlaced footage does have its place. Sporting events and any live-action video looks much smoother with a refresh rate of 60Hz compared to progressive content at 30Hz - at least here in North America anyways. I find a lot of times HD channels are compressed differently depending on the channel, and the service provider you have.

[KevL]

Have done some investigation of dinterlacing setup on my system with Nvidia PureVideo Decoder and ATI Catalyst 8.4 using Pal Format SD signals direct from my TV card in MP.

I can switch off deinterlacing in the video driver altogether and the picture quality is unchanged - which means that the decoder must be doing the deinterlacing and the video card driver is not doing it (when set to auto).

I have also experimented with the deinterlace settings in the Pure Vieo decoder, trying various options and none seemed to get rid of the slight occasional judder in normal playback or the gross judder apparent in the moving text ticker at the bottom of the Bloomberg Channel screen. The Pure video decoder has no option not to deinterlace (I think) so I havnen't been able to try it set to off and letting the video driver do it instead.


I think I'm now ready to try the FFDshow decoder/deinterlace setup to see if this gives me a better picture. Given I'm stuggling with the settings on simple MPEG decoder and Video card then given the number of options avaliable in FFDShow - I might be some time. :-)

@BigJ, Many thanks for the recommendation but on my setup I'm fairly sure bilinear filtering actually degrades picture quality - though this might be to do with the other settings being wrong elsewhere. On my setup having this filtering enabled seems to make the picture over filtered. Faces seem smoother like everyone has thick make-up on or as if they have been airbrushed to remove wrinkles etc. Like I say this might be due to some wrong setting elsewhere so I will bear it in mind when I've got rid of judder etc.


Kev