OTish - Transfer Rates

Veggie_Dave wrote on 4/1/2006, 4:10 AM
This might be an odd question, but here goes...

Is there an accepted transfer rate for MPG2 that replicates the
equivalent broadcast quality for PAL and NTSC TV?

I've probably not asked the question very well, but what I need to do is
recreate how much picture loss there is between something mastered down
to DVCam/Digi Beta and when it's broadcasted.

Comments

johnmeyer wrote on 4/1/2006, 9:50 AM
This is probably not entirely relevant, but you might find what you are looking for at mpeg.org:

mpeg.org (Document describing DVD spec and maximum bitrates)

I don't think there is a defined quality standard that must be met. You can see this for yourself if you watch DirecTV (or Dish). Some channels look yuucky (technical term) because the compression is set too high, others look great.

Also, there are dozens of things that can make an MPEG file look great or lousy, and bitrate is just one of them. If you have any one of the external MPEG encoders and look at the dozens of different settings, and you'll see what I mean.

Finally, a HUGE part of getting great encodes is the work done on the video prior to encoding. Noisy video should be "de-noised," and any material that was previously telecined (from film to 29.97 NTSC) must be inverse telecined.


MPEG Encoding Guide



Veggie_Dave wrote on 4/1/2006, 1:36 PM
Sorry John, I didn't explain my question properly.

I'm looking for a bit rate setting for MPG2 that will give me an equivalent picture to that of a compressed TV broadcast.

I'm doing some odd blurring effects, but as it's specifically for broadcasting, I want to see what it'll look like once it's been compressed by the broadcaster to make sure it doesn't look wrong once it hits peoples' TVs in their living rooms.
johnmeyer wrote on 4/1/2006, 2:15 PM
Well, as I tried to say in my last post, there isn't a standard compression rate. Some broadcasts are compressed at a very low bitrate; others at a high bitrate. There isn't a standard at all. Like I said before, just surf through the satellite channels and you'll see compression artifacts all over the place on some, while others look very good. If you are trying to emulate exactly what a specific broadcaster does on a specific channel, you'll have to call them and get the information. I suspect you'll find that even on a given channel, the compression rate is totally different from one program to another.
Spot|DSE wrote on 4/1/2006, 3:23 PM
Dave,
is the client requiring *you* to compress the footage? That would be the first time I've heard of this from a broadcaster or ad agency. The ad agencies we do work for want the most pristine delivery they can get, and the broadcaster manages the compression, if there is any, depending on where it goes.
riredale wrote on 4/1/2006, 8:06 PM
Are you asking what bitrate you should use when making a DVD so that the MPEG2 looks identical to the original?

If that's what you're asking, there are multiple factors, but I find that, using CinemaCraft, anything above ~7Mb/sec is transparent i.e. no artifacts of any sort.
johnmeyer wrote on 4/1/2006, 8:47 PM
I think what he wants to do is to approximate what will happen to the video when the broadcaster does the compression. That way he will no in advance if there are going to be any surprises.

Veggie_Dave wrote on 4/2/2006, 5:46 AM
> That way he will know in advance if there are going to be any surprises.

Yep, that's exactly it.
JJKizak wrote on 4/2/2006, 6:50 AM
From all of the data I have seen by TV Broadcast engineers explaining prodedures some of them download at 24 megs and others download at 49 megs from satellite feeds then broadcast it OTA. On the SD channels they tend to cheat a lot. Remember this is what I read, don't know the how's or why's.

JJK
johnmeyer wrote on 4/2/2006, 10:41 AM
download at 24 megs and others download at 49 megs from satellite feeds

I don't think those numbers refer to encoding rates -- in fact, I'm sure they don't.
Veggie_Dave wrote on 4/3/2006, 4:57 PM
Well, I'm still none the wiser. Friends who do programming at Bravo are trying to find an answer for me, but apparently it's something that broadcasters don't like to make public.

Not sure why...

If I ever get an answer I'll post it up as it may help someone else one day, too.
kimgr wrote on 4/4/2006, 11:55 AM
My cable company says they transmit @ 5Mb/sec per channel.
This is in Denmark, so it's in PAL.
Some of the satelite channels relayed thru the the cable network are clearly transmitted at a much lower rate. I'm guessing at around 3Mb/sec.

Kim.
Veggie_Dave wrote on 4/5/2006, 6:02 AM
You absolute star!

Thank you very, very much indeed.
johnmeyer wrote on 4/5/2006, 8:34 AM
The 3 MBs and 5MBs are interesting numbers, but tell you very little about what YOUR broadcaster is going to do with YOUR video. The range is likely even wider than 3-5. Do a Google search and you'll see what I mean.