Ask questions to Compression Engineer insider "drmpeg"

[iceman]

This thread is dedicated to asking questions of industry insider "drmpeg" (Compression Engineer insider) who has graciously taken the time to participate here. drmpeg and all our insiders do this out of their free time and to try to keep us informed to their best abilities, and therefore are to be treated with respect and courtesy.

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drmpeg - Compression Engineer - Track posts

[irfoton]

drmpeg,
I asked this in the "Judgement Day" thread but I'm sure this was overcome by the amount of posts.

As HD takes hold and begins to eclipse DVD, how will compressionists be trained? There appears to be more choices than ever for HD. Which codec is the most forgiving? Which provides the best results in the least amount of effort? Which provides the best results when you have all the money and time in the world?

Thanks

[scott1256ca]

Have you done any, or are aware of any side by side comparisons of VC-1 vs. AVC at BD bitrates? If so, can you elaborate on the pros and cons of each?
Are there any hard "this one is better at these bitrates" types of statements you can make?

Thanks

[scott1256ca]

As a followup to my post, how close are either of these codecs to "set it and forget it" when it comes to encoding a 2 hr. 1.85 movie?
Any expectations on when this will be doable with uniformly excellent results, or is that still quite a ways off? Which of the 2 codecs seems to have more room for future growth in this area?

Thanks

[DaViD Boulet]

we see a lot of HD DVD/Amir-speak suggesting that the bit-rates on BD above 20mbps are not needed for video transparency.

Can you comment? Even if transparency can be acheived by careful compresson, are there cost-savings with making things easier by opening up the bit-rate during encoding? Do AVC and VC-1 behave similarly at the various bit-rate levels? Are there advantages with one over the other in different applications?

[PaulGo]

Along the same theme - Now that Warner is going Blu-ray exclusive do you see them upping the bitrate of the VC-1 codec (will it do and good?) or do yousee them going to AVC. Would their be a difference in picture quality (for the better) if they switched?

[drmpeg]

Originally Posted by irfoton

drmpeg,
I asked this in the "Judgement Day" thread but I'm sure this was overcome by the amount of posts.

As HD takes hold and begins to eclipse DVD, how will compressionists be trained? There appears to be more choices than ever for HD. Which codec is the most forgiving? Which provides the best results in the least amount of effort? Which provides the best results when you have all the money and time in the world?

Thanks

To be honest, I don't have much exposure to compressionists, since my background is almost entirely in real-time encoders for broadcast applications.

As for codecs, it's very difficult to compare VC-1 against H.264 in a pure apples to apples fashion. The problem is that you can only evaluate encoder implementations of each standard. There are many algorithms, techniques and tricks (also known as "secret sauce") that are outside of the codec standard that encoder developers can put in their product.

The best encoders are the result of a lot of time and effort. That's why Microsoft's VC-1 encoder does so well. MS was willing to spend the time and effort to make a great authoring encoder. Of course, since VC-1 was pretty much rejected in the broadcast space, MS more or less had to create a good authoring encoder since blue laser was the last large segment they could enter.

In the H.264 space, many of the very best compression folks are working on real-time broadcast encoders and blue laser authoring encoders are pretty much being ignored by these companies. There's just not enough volume to justify the R&D (one encoder can create a lot of titles). We're lucky that at least a few companies (like Panasonic) were willing to develop an H.264 authoring encoder. BTW, Panasonic was very active in the development of the H.264 standard. Almost all of the the High Profile features (like 8x8 transform and scaling matrices) were suggested by them.

Ron

[drmpeg]

Originally Posted by scott1256ca

Have you done any, or are aware of any side by side comparisons of VC-1 vs. AVC at BD bitrates? If so, can you elaborate on the pros and cons of each?
Are there any hard "this one is better at these bitrates" types of statements you can make?

Thanks

Well, the studios do this all the time, but the results never get published. As for doing a public "shootout", there's many pitfalls to the concept. First, there's very little copyright free uncompressed content available. Certainly no full length movies. Even when there is some content available (like Elephants Dream), everyone complains it's not a real movie.

Second, there's always the "you didn't use our latest and greatest encoder" excuse. Since there's always another latest and greatest on the way, it's very easy to trivialize the results of any shootout.

I've seen some of the statements made on AVS about AVC looking better at high bitrates and VC-1 looking better at low bitrates. At low bitrates, the encoder implementation will most likely overshadow any particular codec features. At high bitrates, H.264 may have an advantage since the loop filter can be entirely disabled (which seems to be the case for many current movies) and more high frequency detail can be coded by the use of flatter scaling matrices. However, my guess is that both codecs look remarkably alike at high bitrates.

Ron

[drmpeg]

Originally Posted by scott1256ca

As a followup to my post, how close are either of these codecs to "set it and forget it" when it comes to encoding a 2 hr. 1.85 movie?
Any expectations on when this will be doable with uniformly excellent results, or is that still quite a ways off? Which of the 2 codecs seems to have more room for future growth in this area?

Thanks

Creating a good multi-pass encoder is more about gathering the most useful statistics during the first pass and then applying a heuristic algorithm to those statistics that can arrive at a constant quality encode (for a particular average and peak bitrate). It's fairly codec independent (it's more of an entropy issue), although the algorithm does have to have a good idea of the codecs quality versus bitrate curve.

There's no doubt that higher average and especially peak bitrate make things easier. Both VC-1 and H.264 benefit from the higher rates available on Blu-ray.

As for future growth, there's no doubt that H.264 offers more areas to explore. MPEG-2 saw incremental gains every year over the last 12 years, and it's expected that H.264 will be very much the same.

Ron

[aygie]

Hi Ron

do you have any involvement with UK TV at all?

[drmpeg]

Originally Posted by DaViD Boulet

we see a lot of HD DVD/Amir-speak suggesting that the bit-rates on BD above 20mbps are not needed for video transparency.

Can you comment? Even if transparency can be achieved by careful compression, are there cost-savings with making things easier by opening up the bit-rate during encoding? Do AVC and VC-1 behave similarly at the various bit-rate levels? Are there advantages with one over the other in different applications?

Depends on where your coming from. From a broadcast perspective, bitrates over 20 Mbps are astronomical. Everybody is trying to develop encoders that will go as low as possible and anything over 10 Mbps is considered high.

But blue laser is a different animal. IMHO, there's no reason not to use all the available bits on the medium (unless the movie is just too short or not complex enough). Higher bitrates are always better than lower bitrates. You may not be able to perceive the difference, but why worry about that if you have the bit budget?

Although I work at an H.264 company and know more about it, there's no doubt that VC-1 is an excellent codec. Given some of the high bitrate encodes we've seen lately (like Ratatouille), it's seems like a waste of energy trying to declare a winner. The real winner is the consumer. You're getting some truly "transparent" encodes (aside from 8-bit and 4:2:0 issues) with both codecs, and you should be ecstatic that the blue laser formats and advanced codecs make this possible.

Ron

[dialog_gvf]

Originally Posted by drmpeg

Depends on where your coming from. From a broadcast perspective, bitrates over 20 Mbps are astronomical. Everybody is trying to develop encoders that will go as low as possible and anything over 10 Mbps is considered high.

What is broadcast in your context? OTA MPEG-2 HD @ 10Mbps? Is that what they are trying to accomplish, freeing up the other half of the channel for multi-casting?

We know satellite is going MPEG4. Is cable destined for that as well?

Gary

[WickyWoo]

Depends on where your coming from. From a broadcast perspective, bitrates over 20 Mbps are astronomical. Everybody is trying to develop encoders that will go as low as possible and anything over 10 Mbps is considered high.

They look terrible too. Honestly the Fox 720p broadcasts here in Philly are the best because they aren't shoving 3 channels in the space, and because it's 720p they can devote all the bits to it. No nasty DVNR or artifacting, best non-disc HD video I've seen period

[drmpeg]

Originally Posted by dialog_gvf

What is broadcast in your context? OTA MPEG-2 HD @ 10Mbps? Is that what they are trying to accomplish, freeing up the other half of the channel for multi-casting?

We know satellite is going MPEG4. Is cable destined for that as well?

Gary

Anything that uses a real-time encoder. Right now, satellite is the major user of H.264 real-time encoders. IPTV will probably be next, followed by cable. ATSC will be the last.

Cable will have to go to H.264 eventually because of 1080p@60. I know there's a lot of naysayers about 1080p@60, but it's going to happen, and soon. This whitepaper claims that 1080p@60 only takes 20% more bandwidth.

http://www.ambarella.com/docs/1080p60.pdf

Ron

[scragham]

Originally Posted by WickyWoo

They look terrible too. Honestly the Fox 720p broadcasts here in Philly are the best because they aren't shoving 3 channels in the space, and because it's 720p they can devote all the bits to it. No nasty DVNR or artifacting, best non-disc HD video I've seen period

agreed. nbc, abc and cbs all look like ass. for some reason, nbc looks especially bad.

[drmpeg]

Originally Posted by WickyWoo

They look terrible too. Honestly the Fox 720p broadcasts here in Philly are the best because they aren't shoving 3 channels in the space, and because it's 720p they can devote all the bits to it. No nasty DVNR or artifacting, best non-disc HD video I've seen period

The sad part about OTA is that many stations are still using the same MPEG-2 encoder they bought in 1998 (especially if you're in a major market).

On the AVSForum HDTV Programming section, a lot of folks complain about NBC. Here in Silicon Valley, NBC looks fine because they have new encoders, and the weather sub-channel only gets 1.5 Mbps or so (and still looks okay).

Ron

[fronn]

Originally Posted by drmpeg

The sad part about OTA is that many stations are still using the same MPEG-2 encoder they bought in 1998 (especially if you're in a major market).

On the AVSForum HDTV Programming section, a lot of folks complain about NBC. Here in Silicon Valley, NBC looks fine because they have new encoders, and the weather sub-channel only gets 1.5 Mbps or so (and still looks okay).

Ron

Hi Ron,

Is there any sort of push for them to upgrade or are they not likely to upgrade until they decide to switch to an H.264 encoder? (and then proceed to use that same encoder for 10 years)

Is upgrading encoders a large endeavor or are these stations just lazy and unwilling want to drop the cash for a smaller segment of the market? Additionally (I'm not sure if any of this is really in your realm), are they likely to be more caring about their broadcast quality when HD becomes more mainstream... or is this just how it goes for some of the stations?

Sorry for the large amount of questions, but they all kind of relate.

Ultimately, I'm curious if the situation with HD broadcast/cable/sat quality likely to actually get better over time, or are we destined to a land of mediocrity where it is at it's best right now (as more channels are stuffed into a fixed amount of bandwidth, quality may even go down?)... Is there a push to make the quality better over the next several years and we just so happen to be in a time where adding channels is more important than channel quality, or are they quite content with the quality we have now?

[gand41f]

Originally Posted by drmpeg

The sad part about OTA is that many stations are still using the same MPEG-2 encoder they bought in 1998 (especially if you're in a major market).

On the AVSForum HDTV Programming section, a lot of folks complain about NBC. Here in Silicon Valley, NBC looks fine because they have new encoders, and the weather sub-channel only gets 1.5 Mbps or so (and still looks okay).

Ron

Are you talking about NBC11/KNTV? That's funny...I always used to think they are the worst. Now that I have a 1080p TV, ABC and Fox look bad, the latter even though it doesn't have any sub-channels. This might have something to do with my particular TV not having a dot by dot mode for 720p ATSC signals.

On the other hand, CBS looks fabulous both on my old and new TV. On my old TV it was CBS > Fox > ABC > NBC (the latter two have subchannels), on my new TV it is CBS > NBC > Fox > ABC although NBC looks pretty bad when there is lots of movement. One particular moment I remember is the opening ceremony of the Winter Olympics in Turin, the flame was looking absolutely terrible with pixellation artifacts. Did they get a new encoder since then?

enjoy
gandalf

[WickyWoo]

Our NBC feed is absolutely the worst. I was watching Las Vegas last week and every face was a smeary mess

[Teazle]

Originally Posted by drmpeg

Cable will have to go to H.264 eventually because of 1080p@60. I know there's a lot of naysayers about 1080p@60, but it's going to happen, and soon. This whitepaper claims that 1080p@60 only takes 20% more bandwidth.

http://www.ambarella.com/docs/1080p60.pdf

Wow, very exciting stuff ... Thank you for these fascinating and informative contributions!