Maximum bitrate question

[FakerZ]

I found in some SVCD guides that max video svcd bitrate is 2600, and in a thread posted here (can't remember wich one) I saw something about a 2350 (or something approaching) max bitrate !

What's the real max video bitrate for an SVCD ?

[da franksta]

it really depends on your stand alone player. you can check vcdhelp.com to see what's known about yours.

2600 sounds more like max total bitrate

[FakerZ]

Then I should use 2600-128=2472 if I encode audio at 128 ?

[da franksta]

if your player can handle 2600 the answer is yes

[FakerZ]

Thanks :)

[poopity poop]

hey dude...2600max for an SVCD player...do you have an SVCD player?

I'm sure you have a DVD player can handle MUCH more than 2600Kbps, now if someone would only anser question 2 of my thread a couple days ago:
http://forum.doom9.org/showthread.php?s=&threadid=17979

[FakerZ]

No, I don't have an SVCD player, but bitrate issues can cause playback problems (you should know, because it's what happened you when you tried using a 8000 bitrate as you said in your thread).
I just want to stay compliant with the standard so my SVCD will play correctly on most players.

[poopity poop]

yeah I did try 4500Kbps and that worked well, I just know the maximum for the DVD player and prolly most will be somewhere in that range

[Pko]

Max bitrate as described in the standard of SVCD has some "flavors":

maximum VIDEO ALONE is 2600
maxumum AUDIO ALONE (all audio streams combined) is 384
Maximum TOTAL (audio+video+subtitles+whatever) is 2748

if your audio is at 224, your video can be as high as 2524, but since in multiplexing some space (-> bitrate) is wasted, it is slightly lower (perhaps 2510...). You can calculate the exact value with the utility "FitCD" that you can download from doom9.org

if your audio is at 112, your video could be at 2636, but since the video cannot be higher than 2600, that is the maximum.

If you want to have 2 audio streams at 224, bad luck, because you cannot: 224+224=448; maximum for audio is 384. It can be 224+160, or 192+192 or many other combinations, but 224+224 is forbidden.

Of course, all that is what the standard says... I think, unless you have some very specific reasons, you should stick to the standard; some players cannot reach the standard, but that are players that should be avoided. Your encodes should not be handicapped because somewhere in the world some guy has a junk player that can only reach 2000Kbps bitrate maximum, don't you think?

And also, you should not go further than the standard, perhaps the player you have today can play to 3000Kbps, but many other cannot; the standard exists precisely to have a common ground for everyone.

[FakerZ]

THAT IS AN ANSWER ! Wow !

Thanks a lot lot lot !!!

I'll save this as a .txt file because it is THE info I needed.

:):):)

[adam]

In regards to having 2 audio streams at 224kbits, I think thats still within the standard. I believe that the max audio bitrate of 384kbits only applies to a single stream.

Svcd standard bitrate limits for both video and audio were derived from the speed at which the data could be read from a cd, ie: 2x. Even if the cd contains audio which adds up to more than 384kbits, its still only playing, in this case, 224kbits of audio at any given time.

I may be completely wrong about this but with 2 audio streams at 224kbits Philips SVCD Verifier still says it complies to the SVCD standard, and I've never found a dvd player which couldn't handle it.

Ultimately I guess it really doesn't matter either way since the svcd standard appears to be anything BUT standard. If it plays on your dvd player than thats really all that matters, just don't go too crazy.

[poopity poop]

I looked at a DVD I had with Kenshin on it and did some math:
For a 23 minute episode the entire vob's were 1500mb/episode
With that plugged into DV tool with two audio sources it came out to around 7000Kbps, so that means most DVD players can go at least that high. It would stand to reason that it would be able to read SVCD's at that high, or at least above 4000 which makes SVCD's look perfect.

[ebert]

when using VBR, is that bitrate the maximum average bitrate or the maximum peak bit rate ?

ee.

[Kedirekin]

Most DVD players can't read CDR as fast as DVD. The entire laser mechanism is tuned (mechanically and optically) to read DVDs. Plus the fact that, at a given angular speed, more data will move under the laser pick on a DVD than on a CDR.

So, bottom line, few DVD players will be able read 9.8 mbps from CRD, and many won't even read 4.0 mbps (I know my apex won't - I can't even do 3.0 mbps reliably).

@ebert - I believe it is the maximum that you need to worry about for playability. If the max goes above what your player can read (except for maybe very short bursts), you'll get playback problems.

[Pko]

Originally posted by adam
In regards to having 2 audio streams at 224kbits, I think thats still within the standard. I believe that the max audio bitrate of 384kbits only applies to a single stream.


I do not think so... maximum bitrate of an MPEG-I layer 2 stream is 320kbps... Nothing related to SVCD, is just a limitation imposed by the MPEG standards definition... So, it will not have any meaning to say that the stream in SVCD cannot be higher than 384 when in fact it cannot be higher of 320 in any case!

But as you said, if all the players play it, it is a moot point :-)

I think that the audio limitations are not very important, because what SVCD is usually crying for is VIDEO bitrate. For example, the 128 audio is (IMO) usually less annoying than the 2600 video... and 2600 is as high as you can go while 128 is a middle setting.

I've seen professional DVDs that had MP2 at 224 while the video went at 4000-6000! MP2 at 192 is usual in DVB too, and the video there is in the 3000-5000 range.

[FakerZ]

I agree with Pko, Video bitrate is THE thing we need to preserve. I almost always encode audio at 112 to gain a few more space for video.

[trott]

If you would:
http://www.cdrinfo.com/articles/svcd/
is _the_ link describing the official specs...
In brief: audio: between 64 and 384 kbit/sec, video: up till 2600 kbit/sec, however: total bitrate should not exceed 2.8 Mbit/sec. It'll also explain the whole thing with the svcd scan offsets, and those infamous underflow errors you can get with bbmpeg muxing.
Something I wonder: this document states: audio bitrate: may vary from frame to frame. Does this mean you can create variable bitrate audio for svcd too?

[FakerZ]

What does this "underflow error" really mean ?

[trott]

Originally posted by FakerZ
What does this "underflow error" really mean ?

From the above pages:


Synchronization among the Elementary streams is accomplished with Presentation Time Stamps (PTS) in the Program Stream in reference to a common System Clock Reference (SCR). These time-stamps describe the delivery time instances of when a pack is taken from the track buffer and payload is extracted and placed into the decoder which is associated with the packet ID.


svcd consists of at least 2 streams: 1 video and 1 audio. Presentation time stamps in the stream make sure they're played back in sync. (Makes you wonder how standards-compliant nero's svcd mode can really be, seeing as many people are having trouble creating sync'ed svcd's with nero.)A pts underflow means, therefore, that the audio cannot keep up with the video. I usually find that this is the result of a too-high video bitrate.
I usually encode with cce and find that when I set a certain bitrate as maximum, after checking it with bitrate viewer the stream almost always exceeds this maximum by a quite big amount during complex scenes. Thus, I keep my max bitrate setting at 2400 maximum. This way it almost never goes above 2600...

[Pko]

Originally posted by trott
If you would:
http://www.cdrinfo.com/articles/svcd/
is _the_ link describing the official specs...
In brief: audio: between 64 and 384 kbit/sec, video: up till 2600 kbit/sec, however: total bitrate should not exceed 2.8 Mbit/sec. It'll also explain the whole thing with the svcd scan offsets, and those infamous underflow errors you can get with bbmpeg muxing.
Something I wonder: this document states: audio bitrate: may vary from frame to frame. Does this mean you can create variable bitrate audio for svcd too?

There has been some discussion about this recently here at the forums; I think that means exactly that, that VBR audio is allowed, but it is not 100% clear yet... Also there is the much more complex question of, even if it is standard, the actual stand alone players will support it OK (subtitles is standard, but support is sparse and highly variable).

I plan to do some tests soon. I'm also planning to do some new SVCD tests disks with "advanced" features:

- VBR audio
- Subtitles (SVCD, CVD and both mixed)
- Silent HQ still menues, HQ still menus with sound, moving menus
- Chapters
- Mixed PAL/NTSC/FILM streams
- Non-compliant streams (352x480/576, 48KHz audio, peaks going over standard)

The idea is have some SVCD images to test, so people can download them and report what works and what not (something like "svcdtest3, second stream works, third stream does not on player brand XXXXX model YYY"). So there would be a common ground to compare everything.

One of the things that stops me from preparing them is that I need some decent quality source videos/audios that must be totally copyright free...

[jj59]

Hi PKO a very good idea.

The VCDImager manual gives some info on VBR audiostreams:

1.5.2 Super Video CD
When creating Super Video CD images mpeg-2 vbr streams are expected with a maximum
allowed bit-rate of approximately 2.6 mbits/sec. The following video resolutions are (officially)
supported:
• 480 x 480 @ 29.97 Hz (ntsc).
• 480 x 576 @ 25 Hz (pal).
The audio stream must be mpeg-1 layer II, with a bit-rate ranging from 32 to 384 kbits/sec
bit-rate (i.e. the audio stream is allowed to be vbr!) with up to 2 stereo or 4 mono channels,
or 1 extended mpeg-1/2 multichannel (5+1) surround sound stream.

The SVCDdesigner manual states:
3.2 Audio
Audio can be encoded as MPEG1 or MPEG2. MPEG2 encodong uses a variable bit-rate, which means simple parts of the audio, such as silence, will require very little disc space.
MPEG2 also has a higher sound quality ans gives the possibility of adding a surround sound extension.

One or two audio streams may be included in a sequence item. In a segment item, audio without video is allowed. When a segment of this type is played, the last video frame to be shown before entering the audio only segment will remain on the screen while the audio is playing.

Known SVCD testfiles:

On VCDImager site
PAL and NTSC Multiple audiostreams and OGT CVD subs
http://www.vcdimager.org/pub/vcdimager/examples/test_svcd/
OGT SVCD subs
http://www.vcdimager.org/pub/vcdimager/.testing/svcd_ogt_test_ntsc.zip
There is also a nice demovcd with authoring possibilities
http://www.vcdimager.org/pub/vcdimager/examples/demovcd/

I believe the same files are afaik on vcdhelp
http://www.vcdhelp.com/svcd.htm

For test examples take a look at Video Quality Experts Group. They have some famous 8 seconds testsequences up in these formats
525@60Hz 8 second sequence file size = 699840 x 260 frames = 181958400 bytes
625@50Hz 8 second sequence file size = 829440 x 220 frames = 182476800 bytes
Don't know if they are copyrighted.
Some thumbnails are here
http://www.vqeg.org/thumbnail.html

jj

[adam]

Originally posted by Pko


I do not think so... maximum bitrate of an MPEG-I layer 2 stream is 320kbps... Nothing related to SVCD, is just a limitation imposed by the MPEG standards definition... So, it will not have any meaning to say that the stream in SVCD cannot be higher than 384 when in fact it cannot be higher of 320 in any case!



Sorry to resurrect such an old post but I lost track of this thread until just now.

Pko the limit of 320kbits is for mpeg1 audio layer III, not layer II.
Mpeg1 audio layer II supports from 32-384kbits for stereo signals, which would explain where the svcd standard audio limits came from. http://www.tnt.uni-hannover.de/project/mpeg/audio/#mpeg1

From my experience Philips Svcd Verifier is completely unforgiving. I cannot think of any reason why it would accept two audio streams each encoded at 224kbits unless the svcd standard did also.

I also remember seeing a document at philip's homepage suggesting possible audio encoding scenarios for svcds. Among others totalling more than 384kbits combined, it suggested two audio streams at 384kbits. Unfortunately I think they have removed all references to svcds from their homepage.

I know, these rules only exist on paper but nevertheless, for the sake of argument...I am fairly certain that the the max audio bitrate of 384kbits applies to each stream, not to combined bitrate. Can someone with the official IEC specs back me up on this? I'm too cheap to pay for the shipping costs :)

[novafire]

Any reason why I get the buffer underflow errors on one PC, but not on another. They have the same exact bitrate settings.