[tkrandall]

My layman's understanding is that MPEG-2 takes an uncompressed HD network feed signal of 1+ Gbps and converts it at approximately a 50:1 rate to get to the ~19.39 Mbps compressed rate that is widely considered "full" HD (not HDlite) using a MPEG-2 scheme. I also understand that the ATSC digital protocols using their employed RF techniques in conjunction with MPEG-2 can squeeze just about that much into the 6Mhz slices of spectrum each OTA channel is allocated. Required bandwidth of course varies dependind on the nature of the images/programming.

(1080p/30 (BlueRay or HD DVD) are about twice that much at ~39 Mbps?)


Anyway, my question is, how much less bandwidth does an equivalent video quality stream of data at MPEG-4 take versus an equivalent quality stream using MPEG-2?

Might ATSC ever adopt MPEG-4 for OTA broadcasts (I know, even more new TV sets....)?

 

[Earl Bonovich]

ATSC will not go to MPEG-4 anytime soon.

They are having enough time just getting NTSC shutdown, and everyone over to ATSC. If they did switch the compression... all hell would brake lose again.

As for efficient is MPEG-4 then MPEG-2.... Way to many factors for an exact number. Other then all things being equal.. MPEG-4 will be smaller then MPEG-2....

 

[hombresoto]

Image quality on mp4 is better than it's mp2 counterpart, AND slightly more efficient. A goal was to reduce compression artifacts, with efficiency being the key. Broadcast the first frame, then concentrate on what and how fast the image changes.

 

[litzdog911]

On the HR20 HD DVR, which records both MPEG2 HD and MPEG4 HD video, I think that the MPEG4 file sizes are about half of the MPEG2 size. So, assuming equivalent video quality, MPEG4 HD video is about twice as efficient.

 

[Earl Bonovich]

Image quality on mp4 is better than it's mp2 counterpart, AND slightly more efficient. A goal was to reduce compression artifacts, with efficiency being the key. Broadcast the first frame, then concentrate on what and how fast the image changes.

When starting from the EXACT same source, yes... MPEG-4 tends to be better in PQ then MPEG-2.

But right now, the MPEG-4 is based off the MPEG-2. Thus be definition, it can be no better then equal to in PQ quality.

 

[tkrandall]

Well, it was my understaninding the whole business case for deploying MPEG-4 is not better PQ (which it may indeed be capable of), but the abilty to squeeze more "equivalent HD quality" channels into the same bandwidth. This, for D* and E* is the big objective - more HD channels on their very limited spectrum. The concern for us of course is the risk of them putting too many HD and/or multicast channels out there and overcompressing it all. (we have a local channel in north GA (14) that multicasts four 480i signals on their DTV channel assignment. Just wonderful. I hope that does not represent the future of DTV!)

Anyway, I simply wanted a feel of how many more equivalent HD channels MPEG4 allows over MPEG2 for the DBS providers.

 

[JeffBowser]

Last night I compared my local channel 5 from 3 streams, on the same set. MPEG2, 4, and straight OTA, from the SD newscast. The MPEG4 stream was significantly better than the MPEG2 stream, and almost on par with the OTA stream. I was astounded at the difference (as I am one of the ones that doesn't really see a lot of difference between your so-called "HD-Lite", and full 1920).

 

[HIPAR]

Last night I compared my local channel 5 from 3 streams, on the same set. MPEG2, 4, and straight OTA, from the SD newscast.

Can you elaborate on how you obtained these streams. Was this SD transmitted in HDTV format?

--- CHAS

 

[JeffBowser]

I assume the MPEG4 datastream does not need to be HD, it is merely a datastream encoding, the source can be anything. In this example, I have 3 sources for my local channels - two from DirecTV, and one from OTA. My assumption is one of them is the MPEG2 data stream, and the other is the MPEG4 datastream. The third, of course, is from my antenna. The SD was transmitted in square format (the local news broadcast)