Is there any FCC law that gives the minimum bit rate for MPEG2 streaming? Local stations are moving to HiDef and now I see a lot more squares. Every fast scene is filled with little squares that it looks like internet streaming.
Is our future seeing little squares!!!
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HD is not "Free of little squares"(macroblocking/compression artifacts) If the source(say, a local station which is multicasting) isn't giving enough bandwidth to HD, and instead is allocating that bandwidth to other things, such as multicasting/datacasting(beyond any available "oppurtunistic" bandwidth).
Unfortuently, for the most part HD+Multicasting doesn't work well together(at the same time), but unfortunetly, many stations are doing it ...
Unfortuently, for the most part HD+Multicasting doesn't work well together(at the same time), but unfortunetly, many stations are doing it ...
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You've got it backwards - the mpeg encoding (like jpeg in some ways) uses blocks (squares in your terminology) of pixels! They are not spending enough bits to define the content of the squares (blocks of data) because they are not using enough bandwidth. It's not specific to HD - check out Fox Sports World on Dish - not much better, some of the time, than streaming video from the 'net.
Andy
| Originally posted by Xavier it is wasting bits on squares!!!. |
Andy
HDTV isn't mandated, so there isn't going to be a mandate for an associated bitrate. And not only is multicast allowed, but they are now considering must-carry (on cable) for multicast channels.
If your HD signal looks that bad, complain to the local affiliate. Certainly multicasting can cause these problems, but affiliates aren't going to stop if no one complains. Our local affiliate dropped a 3rd multicasting signal after lots of complaints.
If your HD signal looks that bad, complain to the local affiliate. Certainly multicasting can cause these problems, but affiliates aren't going to stop if no one complains. Our local affiliate dropped a 3rd multicasting signal after lots of complaints.
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Really? Is the HD picture better now? I haven't watched them in months, but I got pretty sick of the picture quality. Last year's Grammies were about the last straw for me.
| Originally posted by bdb If your HD signal looks that bad, complain to the local affiliate. Certainly multicasting can cause these problems, but affiliates aren't going to stop if no one complains. Our local affiliate dropped a 3rd multicasting signal after lots of complaints. |
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You are in the extreme minority of those who have the kinds of problems you are talking about. Outside of rare moments of pixilization HD for me and most others is incredible and without any flaws that you are experiencing. If ALL you local HD channels have these problems then either your equipment is faulty or mis-configured, you are to far away from the transmitters and have a low signal, or your local channels have a conspiracy to get you to hate HD!
For those of us in the Chicagoland area last years Grammys were absolutely outstanding in both video and audio!
| Originally posted by BarryO Really? Is the HD picture better now? I haven't watched them in months, but I got pretty sick of the picture quality. Last year's Grammies were about the last straw for me. |
For those of us in the Chicagoland area last years Grammys were absolutely outstanding in both video and audio!
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Macroblocking in fast scenes indicates the bitrate used by the station is too low, especially if they are multicasting. For 1080i HD they need to allocate the entire 19.2Mb/sec bitrate fot one HD channel, even then it could still block-out in extreme cases. 720p is more forgiving it can sustain one SD sub-channel. The WB network doesn't supply enough bitrate for HD programs so their programs like Smallville have serious macro-blocking problems on many scenes.
Interesting this thread popped up. I was wondering the other day while watching a HD show, if MPEG4 or H.264 encoding would result in fewer (none?) blocking problems than the currently used MPEG2?
balazer - Thank you for the terminology clarification. I can google DCT block.
balazer - Thank you for the terminology clarification. I can google DCT block.
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If you read the post carefully, you'll see that bdb was referring to "one local affiliate" in the PDX area. Their HD subchannel is not (or at least was not) "incredible and without any flaws", and as I mentioned their broadcast of the Grammies, with its video-sourced and fast-changing content, was awful. Collegues who have analyzed their bitstream have told me they only allocated 10 Mbps for their HD subchannel. It clearly is not enough.
All other OTA and DBS channels look fine to me.
| Originally posted by FrankS You are in the extreme minority of those who have the kinds of problems you are talking about. Outside of rare moments of pixilization HD for me and most others is incredible and without any flaws that you are experiencing. If ALL you local HD channels have these problems then either your equipment is faulty or mis-configured, you are to far away from the transmitters and have a low signal, or your local channels have a conspiracy to get you to hate HD! For those of us in the Chicagoland area last years Grammys were absolutely outstanding in both video and audio! |
If you read the post carefully, you'll see that bdb was referring to "one local affiliate" in the PDX area. Their HD subchannel is not (or at least was not) "incredible and without any flaws", and as I mentioned their broadcast of the Grammies, with its video-sourced and fast-changing content, was awful. Collegues who have analyzed their bitstream have told me they only allocated 10 Mbps for their HD subchannel. It clearly is not enough.
All other OTA and DBS channels look fine to me.
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We've complained to our local CBS and they will not quit multicasting. Their response is that they need to send an SD feed for those unfortunate souls whose TV's cannot stretch an HD signal. Hogwash! Let them feed their TV an S-Video feed and then stretch it. On SD, it doesn't matter that much PQ-wise if you watch it via S-Video anyway.
As a result, we get much pixelation during HD feeds with any action.
As a result, we get much pixelation during HD feeds with any action.
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I don't think broadcasters will ever move away from MPEG2, but I believe MPEG4/H.264 are wavelet based. They wouldn't block but they would have picture noise more like analog tv noise. At least I think that is how I read it.
| Originally posted by stephenC Interesting this thread popped up. I was wondering the other day while watching a HD show, if MPEG4 or H.264 encoding would result in fewer (none?) blocking problems than the currently used MPEG2? balazer - Thank you for the terminology clarification. I can google DCT block. |
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I see lots of "waterfall" compression artifacts on my local, overcompressed
HDTV signal (KQED, PBS). When you get an entire scene change, the
bitrate of the signal really shows, and yes, it turns into large blocks for
a short time. I know exactly what it looks like, because I have captured
some of it using an HDTV capture card and examined it frame by frame.
| Originally posted by Nitewatchman HD is not "Free of little squares"(macroblocking/compression artifacts) If the source(say, a local station which is multicasting) isn't giving enough bandwidth to HD, and instead is allocating that bandwidth to other things, such as multicasting/datacasting(beyond any available "oppurtunistic" bandwidth). Unfortuently, for the most part HD+Multicasting doesn't work well together(at the same time), but unfortunetly, many stations are doing it ... |
HDTV signal (KQED, PBS). When you get an entire scene change, the
bitrate of the signal really shows, and yes, it turns into large blocks for
a short time. I know exactly what it looks like, because I have captured
some of it using an HDTV capture card and examined it frame by frame.
Alot of us probably have higher resolution displays than many local affiliates have in their control rooms. Either that, or they're watching on 19" PC monitors or 1024x768 plasmas. They probably don't even see the artifacts. ......or they don't care. 
I have a local affiliate which multicasts ABC in 720p, FOX in 480i, and WB in 480i. All look like crap when you get right down to it. I see blocking all the time.
I think the compression standard will eventually improve, at least for pre-recorded media and PC archiving. I hope they use a more efficient codec on HD-DVD, whatever the disk format turns out to be. The networks are really the only ones stuck with MPEG-2, right? Pay TV (Satellite/Cable/Pre-Recorded Content) can always be upgraded to new compression schemes, even the uplinks from HBO too, right?
Sean
I have a local affiliate which multicasts ABC in 720p, FOX in 480i, and WB in 480i. All look like crap when you get right down to it. I see blocking all the time.
I think the compression standard will eventually improve, at least for pre-recorded media and PC archiving. I hope they use a more efficient codec on HD-DVD, whatever the disk format turns out to be. The networks are really the only ones stuck with MPEG-2, right? Pay TV (Satellite/Cable/Pre-Recorded Content) can always be upgraded to new compression schemes, even the uplinks from HBO too, right?
Sean
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Nope, MPEG4 (aka H.263) uses the exact same DCT transform as MPEG-2 but has other qualities that make it more efficient, so it will not block as easily, but if you push the bitrate low enough you will see the exact same artifcats you do with MPEG-2.
H.264 uses a transform other than the DCT, but is still done on blocks (however I believe the blocks are 1/4 the size).
AFAIK, wavelet transforms have not been popular for video compression because of difficulties implementing temporal compression using wavelets. Unlike the block based transform codecs that utilize the same blocks for block-based motion compensation.
| Originally posted by drhill but I believe MPEG4/H.264 are wavelet based. |
H.264 uses a transform other than the DCT, but is still done on blocks (however I believe the blocks are 1/4 the size).
AFAIK, wavelet transforms have not been popular for video compression because of difficulties implementing temporal compression using wavelets. Unlike the block based transform codecs that utilize the same blocks for block-based motion compensation.
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