Avisynth 2.5 real world performance benefits

[scmccarthy]

I understood that MPEG-1 does not have interlaced video, but only progressive. And yes, I don't have access to the specs, but understanding how MPEG-2 is used in real world applications is on an equal footing with understanding the specs. If not a single person actually uses a part of the spec, that part does not exist. Of course, that is an existential philosophy, really:)

Stephen

[Guest]

Originally posted by scmccarthy
I understood that MPEG-1 does not have interlaced video, but only progressive.Correct, but irrelevant to my point. An interlaced frame can be encoded as progressive. It just doesn't compress as well.

[scmccarthy]

@neuron2

It is relevant to my point that MPEG-1 was not used for television. DirecTV must have been sending a progressive signal that the box interleaved. All I meant was that MPEG-2 was upgraded in part to include fieldbased encoding for TVs.

Stephen

[scmccarthy]

@neuron2

OK, a while back you said:Actually the MPEG2 spec defines the color format as one of the following:

4:2:0 Y Cb Cr
4:2:2 Y Cb Cr
4:4:4 Y Cb Cr

Y Cb Cr corresponds to Y U V. 4:2:0 Y Cb Cr corresponds to YV12 and 4:2:2 Y Cb Cr corresponds to YUY2. So it is not true that MPEG must be YV12. The format is specified in the chroma_format field of the sequence extension of the MPEG syntax.This defines the fourcc codes, but sheds little light on MPEG-2. 4:4:4 Y Cb Cr still is not a compression scheme, and therefore would never be used to share data. It must definitely be used in-house at professional MPEG-2 comperssion houses, but they could easily buy the decoder and encoder from the same company, so they would not have to follow the spec. MPEG is for straightening out compatibility issues that cannot exist for a format so little used.

Stephen

[Guest]

Originally posted by scmccarthy
It is relevant to my point that MPEG-1 was not used for television. You are simply wrong about this. It was used initially and during a transition period. I develop DirecTV settop boxes for the industry leading manufacturer of MPEG decoder ICs. I have personal knowledge and experience of it.

As for your following post, I have no idea what you are talking about. The MPEG2 spec specifically allows for 4:4:4 Y Cb Cr. Again you are simply wrong.

[Leolo]

Hi scmccarthy,

I thought that maybe some of the files I have in my hard drive might contain MPEG2-compliant video streams encoded in 4:2:2 chroma format.

However, I quickly realized I was wrong when I read this post:


http://www.linuxtv.org/mailinglists/linux-dvb/2001/01-2001/msg00182.html

To answer the question, Siemens DVB card cannot decode MPEG-2 4:2:2 pictures, because the MPEG decoder is only MainProfile@Main Level.
On the other hand the tuner can receive the signal; and I am now working on a software that allows to capture these 4:2:2 streams and it will then be possible to play them using a software only MPEG player (supporting MPEG 4:2:2). Up to now I was able to capture one second of an EBU broadcast and play it on my PC. But I guess there will be problem with the bitrate - currently the MPEG-2 - 4:2:2 bradcasts (on Eutelsat W3) use 10 or 21 Mbits/s for a single channel!


I'm using a DVB card (Hauppauge WinTV Nexus) which is almost identical to the Siemens one. But I always capture using the standard hardware method (in PVA format, using the MPEG2 decoder chip), so it's impossible that any of my files use the 4:2:2 chroma format. All of them are 4:2:0.

Sorry for the confusion.

Kind regards.

[scmccarthy]

@Leolo

All I ever meant was, mentioning that you are capturing with a DVB card and that's how your mpeg-2 files were produced would have been better. Then someone who knows about DVB cards (not me) might have been able to confirm what color space they use much sooner.

@neuron2

I am not disputing your knowledge, but I am not wrong. My point is, if there is a part of the spec that not a single person has impemented, then from a practical point of view, it does not exist. Some of the spec is more useful than others, to you or to anyone else. So I am curious what type of application would need a 4:4:4 Y Cb Cr encoder. What's its practical application? Who, if anybody, uses that part of the spec?

Stephen