MPEG-2 max bitrate

[Sjakko]

Hi guys,

I need some information on the max bitrate of MPEG-2 video's. Let me explain the situation.

I do quite some tv capturing with my dtv cards (just PAL MPEG2). Because of its great Quick Jump feature I use Cuttermaran to cut some scenes and export them to separate MPEG files. Then I throw them at Corel Videostudio to join them with some nice transitions. Then I'd like to use VideoStudio's MPEG Optimizer to render the result losslessly (well like 99% losslessly, it does have to re-encode the split GOPs and transitions).

Now the problem: the MPEG files Cuttermaran produces all have different max bitrates, so VideoStudio doesn't recognize them as being of the same format and hence can't use the smart render. Changing each video's max bitrate with ReStream solves the problem. But here are my questions:

How do I know what bitrate to use? And what effect does it have? I don't understand what a max bitrate means in this context. I know what it means when you're encoding, but in my situation it's just a tag and doesn't appear to have anything to do with picture quality. Some clarification would be nice. And my last question: is there a command line tool to set the max bitrate (like ReStream does)? That way I can create a batch job. Thank guys.

[edDV]

Max bit rate is usually set by media type or transmission channel. I don't think MPeg2 has a maximum but for HD 1080i video you would probably reach no advantage around 200 Mb/s. Blu-Ray max is ~35-40 Mb/s.

For SD DVD MPeg2 the max is around 9.8 Mb/s.
https://www.videohelp.com/dvd

Broadcast MPeg2 varies by source. If you cap the digital stream, SD is usually between 2.5 and 6 Mb/s. (typical is 3-5).

[edDV]

...But here are my questions:

How do I know what bitrate to use? And what effect does it have? I don't understand what a max bitrate means in this context. I know what it means when you're encoding, but in my situation it's just a tag and doesn't appear to have anything to do with picture quality. Some clarification would be nice. And my last question: is there a command line tool to set the max bitrate (like ReStream does)? That way I can create a batch job. Thank guys.

So are you trying to use "Smart Render" with VBR source? I've only got it to work with CBR or sometimes with source encoded with the same "average bitrate". This was with the Mainconcept full encoder. Video Studio only specs "max bitrate" not average for VBR so I gave up trying to make it work in Video Studio. I did get CBR to work.

[jagabo]

I've created full D1 MPEG 2 video with up to 80,000 kpbs with TMPGEnc Plus set to Main Profile & High Level. TMPGEnc Plus allows up to 15,000 kbps with Main Profile and Main Level. Obviously, neither of these is DVD compatible.

[Cornucopia]

"MPEG2" itself doesn't have a max, but the various levels do (Low level, Main Level, High Level...). LL has a max of 1.85Mbps to stay "valid", IIRC. Main level has a max of 15Mbps. Can't remember high level.
Of course DVD-Video is a SUBSET of that, in that they accept only Low and Main levels, and Main is constrained by the throughput of the disc, so has been lowered to 9.8Mbps.

The #s are in the spec...

Scott

[Sjakko]

So are you trying to use "Smart Render" with VBR source?

Yes I am. When I drop the whole source video in VideoStudio and cut some parts out, smart render (it's called MPEG Optimizer in VideoStudio) does work. But I really want to use Cuttermaran to do the rough cutting before I import the resulting scenes in VideoStudio. It's just that Cuttermaran sets the max bitrate (still don't understand the meaning of setting a bitrate without encoding) to a different value for each scene. That way VideoStudio doesn't understand that these scenes come from the same source and that it can use smart render.

Off course I can change the max bitrate for each scene manually with ReStream, but not before I understand what consequences that has. Would be great if someone could clear that up for me. Forgive me my noobness.

[edDV]

Noobness? You've gone deeper into VS than I have. I was just checking to see if it worked back on version 9.

It seems Cutterman is the problem. It may not be altering the stream but just changing the metadata.

The thing I don't like about VS is this "Max bit rate" vs. the min/average/max used in the full Mainconcept MPeg encoder.

[jagabo]

Cuttermaran sets the max bitrate (still don't understand the meaning of setting a bitrate without encoding)

It's just a hint (a number in the header) for the playback device. "Be prepared to handle bitrates up to ___ kbps."

to a different value for each scene.

Because each scene has a different maximum bitrate within a VBR encoded video. A high motion, highly detailed scene will use a lot of bitrate. A noiseless still shot will use little bitrate.

Off course I can change the max bitrate for each scene manually

Set them all to the highest bitrate found in all the files. Or, if you're making a DVD set them all to a high value like 9800 (about 10000 minus the audio bitrate).

[Sjakko]

Thank you jagabo!
You also happen to know a free cmdline tool to write the max bitrate of mpeg2, like ReStream can? I already found mpgtx to read but also need a tool to write.

[Anonymous4]

12

[minidv2dvd]

dvd total bitrate is limited to ~ 10mbps total. subtract all your audio streams from that and leave a couple hundred for the "just in case"... so if you have 1 pcm audio stream that's 10,000 - 1500 + 200 = 83000kbps for the video bitrate or there abouts. use whatever your total audio bitrate would be in place of the 1500.

[jman98]

Good information!

I'm using ProCoder v3.

If I'm only making DVDs that are 20-30 mins each, should I just go ahead and do a constant bitrate of 9800? Like if size is no issue, is there a chance that I hurt the video by making the bitrate too large? (DURING AN ENCODE)

I have never used ProCoder. However there are 2 reasons why you may not want to do this is you are going to try to make DVDs out of these files with no conversion.
1) Some encoders exceed the maximum bit rate you specify. TMPGenc is notorious for this, but it's not the only one. If your encoder exceeds this value, some DVD authoring programs may refuse to let you make a DVD out of the video because it violates the standards for DVD.
2) Some standalone DVD players are said to have playback problems with bit rates this high. I don't remember any specific models that this it true for, I just remember reading others talk about it.

As a general rule you are right about VBR, although I have a laserdisc to DVD conversion I did that was about 70 minutes and I used CBR video with it to keep things simple. When your video bit rate for DVD exceeds 8000, there doesn't seem to be much to gain by going above that. In other words, you probably can't tell the difference between video encoded at 8000 and video encoded at 8500 or 9000.

[Anonymous4]

12

[halsboss]

jeepers things seem hard that way. I use Video ReDo TV Suite (very cheap)... cuts frame accurately and joins things easily and can re-code where necessary ... built for TV editing ... and NO FUSS...

[noemi7]

I made a few test with Video Studio X2 Pro, and it is NOT software for lossless authoring. No matter what setting and source you choose it always meddles with the original stream, even if there no joints and/or transitions. This apply to MP2 audio which is the most common audio format among European TV channels.

[Sjakko]

I made a few test with Video Studio X2 Pro, and it is NOT software for lossless authoring. No matter what setting and source you choose it always meddles with the original stream, even if there no joints and/or transitions. This apply to MP2 audio which is the most common audio format among European TV channels.

I think you're doing something wrong then 'cause it does have a smart render feature. Check VideoStudio's MPEG Optimizer (Corel documentation).

[lordsmurf]

384k AC3 2/0 is considered "better than transparent" to uncompressed stereo audio. There's no reason to not use it, unless your audio is simply full of high frequencies (usually hiss/noise) that would create artifacts.