To QPel/GMC/Trellis or not?

[dvwannab]

Very confused XviD experiment student needs your help to clear up confusion (or hope so).

I have read a few XviD guides and many posts about QPel, GMC, Trellis, I am confused.

My intention is to encode VHS, TV and DVD rips to XviD, using high bitrate 1600 - 2200 kbps video and 128 mp3 audio, put on DVD-R and play in my set-top Lite-On LVD-2002 DVD/DivX player.

Is it advisable to use QPel, GMC and Trellis in my encodes and have it compatible with my set-top player? Does it really help your video by using these, when you are using a relatively high bitrate?

I hope not to get any ......"Try it and let us know".....responses. I'm much too lazy for that :D

Thanks.

[Manao]

Trellis doesn't change the way the decoder will decode the video, so you can use it without worrying.

QPel and GMC, in the other hand, increase the work of the decoder. In that case, the (online) documentation of your setupbox will (should) say whether they can be used or not.

But...

You're aiming at high bitrates, and setupboxes don't like high bitrates ( more data to decode -> more work ), so in that case, I'd say not to use GMC & QPel.

Also, since you use high bitrates, I'd advise you to get XviD v1.1 and to use the VBV buffer, in order not to achieve too high bitrates which could make your video stutter even without QPel & GMC.

[akupenguin]

Short answers:
Trellis is always good.
Qpel tends to be good for compression, but I can't say whether your set-top supports it.
GMC probably won't work in a set-top.

[gotaserena]

And, depending on your capture process, you may find that even 2200kbps is not enough for q=2 at full D1.

[dvwannab]

Originally posted by Manao

Also, since you use high bitrates, I'd advise you to get XviD v1.1 and to use the VBV buffer, in order not to achieve too high bitrates which could make your video stutter even without QPel & GMC.

I am using the XviD version in the latest Gordian Knot Codec Pack, I believe v1.0.2. I'll search for the v1.1.

Originally posted by gotaserena
And, depending on your capture process, you may find that even 2200kbps is not enough for q=2 at full D1.

I capture at 720x480. TV is resized to something like 512x384. Old VHS and camcorder around 480x352, depending on the condition of the source. Sometimes I go to 512x384. All deinterlaced (kernel or tomsmocomp). DVD usual keep AR and go around 2300 kbps + 128 mp3, and that looks great.

Ok, so, the consensus is
Trellis = good
GMC/QPel = not recommended

[crusty]

I capture at 720x480. TV is resized to something like 512x384. Old VHS and camcorder around 480x352, depending on the condition of the source. Sometimes I go to 512x384. All deinterlaced (kernel or tomsmocomp). DVD usual keep AR and go around 2300 kbps + 128 mp3, and that looks great.


Simple answer for standalone DVD-players in general: Don't use Qpel, GMC or more than 1 B-frame. These are certainly options that are not compatible with DivX. Most standalone players that offer some support for MPEG-4 (You know, DivX, XviD, 3ivX etc.) usually only support DivX.

For some bizarre reason most manufacturers fancy supporting DivX much more than XviD. By making your encode DivX-compatible you have a bigger chance of compatibility. Also, if they do manage to make an upgraded firmware, it usually supports a newer version of DivX and not XviD.

I don't know the specifics for your player, a link to it's features would come in handy.

For 480x352 and 512x384 2300 Kbps is way overkill. If I were you I'd go for better audio quality. Don't use VBR (Variable BitRate), it's not part of the official mp3 spec. Instead go for something like 192 CBR (Constant BitRate).

That way, if you get a better hifi-set, you won't bash your head against the wall for limiting your audio quality. Also, for many TV-rips it's good enough to encode your audio in mono (twice the bitrate...nice). Just check the TV-guide if a program is in stereo or not.

Hope this helps.
Cheers,
Crusty

[akupenguin]

Originally posted by crusty
Also, for many TV-rips it's good enough to encode your audio in mono (twice the bitrate...nice). Just check the TV-guide if a program is in stereo or not.
Nitpick: The difference between mono encoded as stereo and mono encoded as mono is much less than 2x bitrate per channel. You do save some bitrate from not encoding two copies of the analogue noise, but J-stereo does a decent job of removing true redundancy between channels.

[gotaserena]

Originally posted by crusty
For 480x352 and 512x384 2300 Kbps is way overkill.

I know from experience that this is exactly what a analogue source through a capture card asks. And this after heavy filtering. While it's true that taking 100kbps from video to audio won't hit the quality significantly, it's also true that in captures one usually deals with sources not as clean as DVDs.

Sometimes you can get away in 512x384 or smaller with 2 B-VOPs. Trellis is almost always good, some other options (lumi-adaptative quant, chroma opt) are harmless. Qpel is usually not supported (it doesn't help much with dirty material anyways) and GMC is a no-no, although some chips support the useless 1-point version found in DivX, not XviD's.

[Manao]

Qpel [...] doesn't help much with dirty material anywaysFrom my experience, I'd tend to disagree. But I wouldn't use it in that specific case either, as stated before.

[ripper64]

Originally posted by Manao
Trellis doesn't change the way the decoder will decode the video, so you can use it without worrying.And what about different quantization matrices, will they change the way the decoder will decode the video?

[stephanV]

Originally posted by crusty
Don't use VBR (Variable BitRate), it's not part of the official mp3 spec.

O yes it is, that why each MP3 frame has its own header... :)

@ripper64: yes they do, i believe on a DivX device only H.263 is supported (or only has to be supported)

[Manao]

Yes and no. Yes, because the decoding for h263 and mpeg is different. No because if the decoder support mpeg decoding, it should support all mpeg custom matrices ( well i only say should, because there are decoders which don't support custom matrices with coefficients under 16 )

Trellis in itself doesn't change the decoder's behavior toward custom matrices.

[ripper64]

H263 and SP/ASP are the same right?

So, as XviD uses MPEG Quantization, it doesn't comply to the Advanced Simple Profile anymore?

Could somebody please explain those things to me, because I'm confused about all those terms.

Or should I start a new thread?

[Manao]

MPEG Quantization is part of ASP ( it's named quantization type I ). Your confusion comes from the DivX profile certification which is different from the MPEG-4 profile and complicates things because it is often said DivX is equivalent to ASP, whereas it is not.

[ripper64]

But H263 and Advanced Simple Profile are the same I believe?

So, why is that quantization type H263 called H263:D as MPEG Quantization also complies to the ASP standard?