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Question of the Day: Have you ever ordered a product online and received a fake knock-off?
Where's my HDTV broadcast?!
- Thread starter ldmelsa
- Start date
arf9999
MyBroadband Member
or very high quality...depending which side of the fence you are sitting on
It largely depends on the size of the file required, and how much the authors want to spend on the compression. If the compression on a DVD is done automatically and the quality is good and it fits on the DVD, there is no reason to tweak the settings to improve the compression efficiency. The fact is that by applying some manual control, and multi pass encoding, you would probably drop the rate to half of what you're getting without any noticeable drop in quality. This can be done by manually specifying and varying the GOP over time. Broadcast video tends to take a more aggressive approach to compression (and sometimes quality!), thus a bouquet of channels will have an average of around 2Mbps for SD (this doesn't mean that each channel has 2Mbps all the time - sometimes it will be higher, other times lower. A 720p HD signal should have about 3 times the picture data.
arf9999
MyBroadband Member
Well partly, except that I'm talking about MPEG2 and you mentioned MPEG4 @ 20Mbps. I think that they are probably stress testing the system at those rates... it should be possible to bring it down considerably without sacrificing quality. I 'spose it also depends on whether it is "live" or recorded content... on-the-fly compression will be less efficient than "packaged" compression...
ldmelsa
Executive Member
It largely depends on the size of the file required, and how much the authors want to spend on the compression. If the compression on a DVD is done automatically and the quality is good and it fits on the DVD, there is no reason to tweak the settings to improve the compression efficiency. The fact is that by applying some manual control, and multi pass encoding, you would probably drop the rate to half of what you're getting without any noticeable drop in quality. This can be done by manually specifying and varying the GOP over time. Broadcast video tends to take a more aggressive approach to compression (and sometimes quality!), thus a bouquet of channels will have an average of around 2Mbps for SD (this doesn't mean that each channel has 2Mbps all the time - sometimes it will be higher, other times lower. A 720p HD signal should have about 3 times the picture data.
I agree with everything you're saying, arf9999. I would just like to add a few more comments.
Firstly, there is a big deference in the bit-rate required for:
1080i50
720p50
720p25
(I'm not mentioning the 1080p standards as they are not broadcast spec. They are only HD-DVD, Blue-ray, video production and so on.)
I've seen some excellent 720p25 at as little as 5Mbps - using VC-1 (WMV9)
But if the temporal resolution, aka refresh rate, is higher, like 720p50 or 1080i50 then a higher bit-rate is needed - the HD broadcasting standard in the US is +-20Mbps or even sometimes 45Mbps, but that's all Mpeg2.
HDV, used on HD handy cams from Sony, Canon use Mpeg2 transport stream at 25Mbps (1080i), and it looks great.
http://www.archive.org/download/HDV_FX1_7/fx7_05.mpg (change the extension to .ts and play with PowerDVD with hardware on.)
With mpeg4 like VC-1 and h264 you will be able to get away with +-10mbps and even lower for 720p25.
Go to http://www.microsoft.com/windows/windowsmedia/musicandvideo/hdvideo/contentshowcase.aspx for HD at low bit-rates using VC-1 codec. Get Super Speedway - it's awesome!
Last edited:
ldmelsa
Executive Member
Hdtv!!!!
HDTV!!!! - It's so cool.
HDTV!!!! - It's so cool.
lewstherin
Senior Member
- Joined
- Jan 8, 2004
- Messages
- 968
- Reaction score
- 20
All 5 Australian free to air channels broadcast in both analogue and digital formats (DVB-T).
Anything produced locally is generally HD (full 1080i) as well as all the latest series (Lost, Heroes, CSI etc etc).
I recently got a HD digital tv card for my PC, and watching that on my monitor blew my mind. The resolution is insanely good for TV, as is the sound.
Whats even more amazing is how good the reception is.
I'm plugged into the exact same TV antenna and every digital channel is crystal clear - whereas the analogue reception through the same connection is average (a little ghosting and striping on a couple of the analogue channels).
To give you an idea of how much space a HD recording takes up, one hour is around 3.3GB when recording the transport stream (i.e. no encoding, just straight dumping).
In terms of the 16:9 vs 4:3, basically when watching a HD channel, anything that is 4:3 is broadcast as is, so you have black space to either side of the width of the 4:3 picture.
Anything produced locally is generally HD (full 1080i) as well as all the latest series (Lost, Heroes, CSI etc etc).
I recently got a HD digital tv card for my PC, and watching that on my monitor blew my mind. The resolution is insanely good for TV, as is the sound.
Whats even more amazing is how good the reception is.
I'm plugged into the exact same TV antenna and every digital channel is crystal clear - whereas the analogue reception through the same connection is average (a little ghosting and striping on a couple of the analogue channels).
To give you an idea of how much space a HD recording takes up, one hour is around 3.3GB when recording the transport stream (i.e. no encoding, just straight dumping).
In terms of the 16:9 vs 4:3, basically when watching a HD channel, anything that is 4:3 is broadcast as is, so you have black space to either side of the width of the 4:3 picture.
Last edited:
ldmelsa
Executive Member
ldmelsa
Executive Member
I've seen some excellent 720p25 at as little as 5Mbps - using VC-1 (WMV9)
But if the temporal resolution, aka refresh rate, is higher, like 720p50 or 1080i50 then a higher bit-rate is needed - the HD broadcasting standard in the US is +-20Mbps or even sometimes 45Mbps, but that's all Mpeg2.
HDV, used on HD handy cams from Sony, Canon use Mpeg2 transport stream at 25Mbps (1080i), and it looks great.
http://www.archive.org/download/HDV_FX1_7/fx7_05.mpg (change the extension to .ts and play with PowerDVD with hardware on.)
With mpeg4 like VC-1 and h264 you will be able to get away with +-10mbps and even lower for 720p25.
Go to http://www.microsoft.com/windows/win...tshowcase.aspx for HD at low bit-rates using VC-1 codec. Get Super Speedway - it's awesome!
But if the temporal resolution, aka refresh rate, is higher, like 720p50 or 1080i50 then a higher bit-rate is needed - the HD broadcasting standard in the US is +-20Mbps or even sometimes 45Mbps, but that's all Mpeg2.
HDV, used on HD handy cams from Sony, Canon use Mpeg2 transport stream at 25Mbps (1080i), and it looks great.
http://www.archive.org/download/HDV_FX1_7/fx7_05.mpg (change the extension to .ts and play with PowerDVD with hardware on.)
With mpeg4 like VC-1 and h264 you will be able to get away with +-10mbps and even lower for 720p25.
Go to http://www.microsoft.com/windows/win...tshowcase.aspx for HD at low bit-rates using VC-1 codec. Get Super Speedway - it's awesome!
ldmelsa
Executive Member
ldmelsa
Executive Member
.Who do you guys think will broadcast the first HDTV content? Be it through fixed line (cable TV - Telkom/Neotel/GTS) or satellite (DSTV/Telkom/???) or SABC/Sentech. Of course, fixed line would require something >= ADSL2 (and the cap?). The shops are packed full of LCD/Plasma HDTV's and the people are buying these things like hotcakes. But where's the content? I'll buy one when I can watch something on it (HD-DVD / Blue-ray / HDTV broadcast).
Eagerly awaiting high definition
56kMan