Average Bitrate for Hd-programming

[raginranger]

Hello,

This is sort of an extension of the "Digital Signals" thread for a few days ago. A couple posters said the theoretical bitrate for TV programs (hd mind you) was 19.2 mbps, but that it is rarely achieved. I was wondering if anyone knew the typical bitrate that you see in an HD show on television, and also the bitrate for an SD show. Just wanting some facts I can use in a conversation. Thanks a ton.

[phloyd]

The bitrates in reality vary even between different locales.

In any case, you will typically see the following for OTA:

CBS/CW - one HD stream, typically 17-18 Mbps average.
NBC - one HD, one SD or weather, typically 15-16 Mbps for the HD
ABC - 720p, often with one SD or weather (or both), typically 14 Mbps
Fox - 720p, often with one SD or weather, typically 10-12 Mbps

These rates are for video only and may be a little out of date and are from memory...

For the HD movie channels, most are initiated as MPEG2 at 14 Mbps or less. I have heard that they do have MPEG4 available for some channels now. Showtime tends to be a little higher than HBO, Cinemax and Starz.

That said, many sources, especially DIRECTV and Dish Network will recompress their channels, often downres to 1440x1080i or even 1280x1080i. Cable is not so often guilty of this but it is not unheard of. Both sat sources are also commonly recoding to or using MPEG4 feeds.

SD I am not so sure about - most of the subchannels for OTA range between 2 and 4 Mbps. I believe that most SD from Sat are only 480x480i.

[raginranger]

So considering what you've said, the average bitrate is basically around 15 mbps which is like a really bad blu transfer. I'm guessing this is why movies like Casino Royale that kick so much ass (25 mbps transfer, just my guess from using the display button on my ps3 and finding the average) look so much better than HD cable.

[phloyd]

There are two factors - one is the codec and the other is the bitrate.

So, AVC at 15 should be better than MPEG2 at 15.

Unfortunately, the sat providers are taking advantage and most of their AVC broadcasts are in the single digit Mbps and 1440x1080i. So they are not increasing the quality, just the channel count... muted yay.

In any case, the only (public) broadcast I know of that is anything close to BD rates is the BShi satellite broadcast in Japan - last I knew they were doing 20-25 Mbps MPEG2.

In general, BD is superior in both codec choice and bitrate, and in the very least solely bitrate when compared to broadcast channels.

Interestingly the CW, CBS and ABC networks distribute to their stations using 30-40 Mbps MPEG2 feeds. One day I will see if those feeds are compatible with BDRs