audio bit rate

[greengiant]

i just wanted to know whats the lowest audio bit rate that i can use

[offline]

in what? tmpgenc? mp3?

Most people using xVCD do not go lower than 128kbps stereo which = 64kps per channel. VCD standard is between 192 & 224 kbps while
SVCD can go up to 384kbps. Also the bitrate is not the total
factor in determining quality - what process you encode the audio
by is also an important factor.

The lowest you can encode is around 52bps I think but this
would sound like a bad AM radio station.

[adam]

Actually the VCD standard is set at 224. Of course virtually no dvd players have problem playing lower even though it makes your vcd non-compliant.

Personally with a decent source I would never go lower than 160kbits. Below this I can hear noticable artifacts and distortion even on basic hardware setups.

For things like Director's commentary I like to make it mono and encode at 64kbits to save room.

[offline]

For Director's comments I like to make it joint stereo and encode at 64k - same space and quality I should think, without hearing audio from one side only which gives me the irits'

[banjazzer]

Personally with a decent source I would never go lower than 160kbits.

I would agree with that. (S)VCD audio is mp2, so (arguably) 160 kbps mp2 is roughly equivalent to 128 kbps mp3 - which I would not really want to drop below.

[postul8or]

If I have a DVD player that can play SVCD and mp3 files would it be possible to encode the audio in mp3 format instead?

I would also be grateful if anyone could give me information or links to informatino about the audio codecs used in TMPEG. How does the mp2 encoder in TMPEG compare to the Lame series of encoders. I would assume that using VBR in Lame would lead to the best music quality. It's an assumption because I really don't know too much about MP2 overall, especially when it comes to VBR issues (can it be done, how good is the quality etc.).

Thanks in advance.

[banjazzer]

You can't use mp3 to encode to VCD or SVCD, so far as I know. Some people prefer to use the External tools option in TMPG, eg using Toolame and SSRC. Personally I never noticed any difference using the internal or external tools for encoding audio, although I always resample any audio first before inputting into TMPG. If you don't do this, it is possibly worth using SSRC as the external re-sampler.

I am not sure why there is an option to use an external tool to encode mp3.

[adam]

No you definitely cannot use mp3 in a vcd or svcd. If you could even find a way to multiplex it there would be no way your dvd player would play it correctly.

There is an option for an mp3 external encoder because TMPGenc can encode to avi. File/output to file/avi.

VBR audio is supported in the SVCD specification but not in the VCD specs, but unfortunately most dvd players seem to have problems playing these in a SVCD. You can try it if you want, but even if your player can handle it, realize that any future player you buy may not.

Personally I can hear a difference between toolame's output and TMPGenc's. You will have to try them both for yourself but the general consensus is that toolame is higher quality.

TMPGenc's frequency rate converter 48kHz->44100kHz apparantly has a bug where it randomly introduces a tinny metallic sound. Otherwise the quality is ok.

Occasionally I will use TMPGenc to encode audio and I always use ssrc and toolame as external encoders. My normal procedure though is to use BeSweet and go straight from ac3 to mp2.

[postul8or]

Do you tend to stick with 224kbps adam and banjazzer or do you go with a different bitrate at times?

[banjazzer]

If I make an xVCD, to fit a movie to one CD, I sometimes drop the audio to 160, but I don't like to go below that. Bear in mind that mp2 at 160kbps is not the same quality as mp3 at 160kbps.

[offline]

In the past I found that low mp2 bit rates (160-128) seemed better in
joint stereo. These days I only use ac3 at 384kbs (or higher)
which means I have to run my SxVCD's/xcDVD's at CVD resolution to
make up for the loss in bandwidth.

However I have never come across a good description of
the real world differences between dual channel, joint stereo
and stereo to the average ear. Anyone done their own experiments?

[xed]

As to the question of whether you can use mp3 audio in a VCD or SVCD, let's be precise here --
[1] Yes, you can _encode_ the audio stream using mp3 when producing a VCD or SVCD, but...
[2] No, most standalone *hardware* DVD players won't _play_ the mp3 audio stream in such a CD-R or DVD.
However, if your goal is play your VCD or SVCD files back on a computer, note that Microsoft Media Player definitely will play back the audio stream in such a VCD or SVCD. I know this for a fact because I've experimented with burning SVCDs with mp3 audio. They play back on a Win98SE computer. The audio doesn't play on most DVD players.
So it really depends which platform you want to play your VCD or SVCD back on.
Software VCD or DVD players seem much more flexible in accepting variants of the strict VCD and SVCD specs. Some folks I know watch DVDs primarily on their computers. If you're one of those folks, you might well want to encode the audio stream into layer 3 (mp3) instead of layer II.
The caveat being that if you later decide you want to play the VCD or SVCD back on a DVD player, you will have to re-encode the audio stream into VCD-compiliant layer II and re-mux the audio (probably will BBMPEG) and then re-burn the VCD or SVCD to get an audio track on your DVD player.

[adam]

I usually use 192kbits stereo for the main audio track and if there is a director's commentary track I encode it in 64kbits mono.

[southside97]

Hi, I have question... I captured a show with virtualdub into AVI 480x480 and audio at 172kb/s, then encoded to SVCD format using TMPG but I lowered the audio rate to 128kb/s to make my file a little smaller to fit on cd.... but what I wanted to know is will I be able to play it in a standalone dvd player or does it have to be encoded at 224kbps? I haven't burned it on cd yet since I want to make sure if it will play or not... if not then I would have to encode the avi file again and change the audio to 224kbps.

[adam]

Svcds support up to 384kbits, so you can go as low as any encoder will allow and your disk will still be compliant, and any hardware player should be able to play it.

Vcds do require 224kbits audio in order to be compliant, but few dvd players have a problem with lower bitrate, whereas higher bitrate may cause a problem. Your dvd player probably will play it fine but technically you are making an xvcd.

[postul8or]

Sometimes I wish that there were BIOS upgrades for DVD players so that you could break logical barriers....like differing from the VCD standard and going with VBR mp3 instead of 224 mp2.

I guess it means the hardware chip needs to be somehow flexible like an EPROM as opposed to a static type of software. Anyone got some more information on how the decoding stuff in DVD players works exactly? I would like to read up on it a bit more and learn about it.

[sterno]

However I have never come across a good description of
the real world differences between dual channel, joint stereo
and stereo to the average ear.

I actually did see a web page that talked about joint stereo, but I honestly have no idea where it was. It's designed to give you better quality than standard stereo at the same bitrate by handling sound that's duplicated on both channels in a more intelligent manner, but (as you noticed) it's only useful at lower bitrates where you're starting to get compression artifacts. Sort of like encoding in NTSCFilm vs. NTSC - joint stereo makes better use of the bitrate, but you won't notice it at a high enough rate because you're not losing much anyway.

One important side effect of joint stereo is that it destroys any Dolby Surround encoding. Most of the time I use 224k and quite often the source has surround sound (and I have a prologic decoder), so I don't use it. I can see where joint stereo would be appropriate with SVCD/XVCD to squeeze a little more on one CD at decent quality, though. But, as always, quality is a subjective thing.

[sterno]

Sometimes I wish that there were BIOS upgrades for DVD players so that you could break logical barriers....like differing from the VCD standard and going with VBR mp3 instead of 224 mp2.

Not that this helps, but some DVD players do have upgradable firmware. They can be upgraded with a firmware image burned to a CD-R. You can download modified firmware to disable macrovision and region locking, enable miniDVD/cDVD, alter background or screen saver images, etc. But VCD with MP3 audio is way beyond anything I've seen, and is quite possibly beyond the capabilities of most current players.

[postul8or]

sterno, you're probably right that what I am asking for is beyond what exists at the moment. I suppose what I'm really asking for is the flexibility that a computer provides but in a DVD player.

[DJRumpy]

Flashing the firmware on a DVD isn't quite that complicated. All it will require these days is a Win32 compatible flash program. Most of them can be done directly in Windows via a gui interface. The types of patches you will see are usually reserved for problems the DVD/CD has with copyright methods, bugs in the firmware, etc. There is only so much they can squeeze onto a firmware chip. The player does what it was designed to do. Remeber it does play all of these formats on your PC. It's the standalones that need a more robust interface.

I know of quite of few people who have moved a PC into the living room, and use the video out's on their video cards, projectors, etc, to bypass all the restrictions built into a standalone.

[vitualis]

One important side effect of joint stereo is that it destroys any Dolby Surround encoding. Most of the time I use 224k and quite often the source has surround sound (and I have a prologic decoder), so I don't use it. I can see where joint stereo would be appropriate with SVCD/XVCD to squeeze a little more on one CD at decent quality, though. But, as always, quality is a subjective thing.

At higher bitrates (e.g., 224 kbit/s CBR), a good MPEG audio encoder would probably not affect the Dolby Surround information to any great degree even when you encode with Joint Stereo.

However, this is a definite risk and I personally only encode using standard stereo (at 224 kbit/s). As you said, at 224 kbit/s using MP2 encoding, there will be little (audible) benefit in using JS encoding over standard stereo.

For those dropping the bitrate for their audio encoding, MP2 does not do as well at lower bitrates like MP3. For example, at a bitrate of 128 kbit/s, MP2 is vastly inferior to a similar MP3 encoding of the same bitrate. Remember, the "quality" of your X/S/VCDs doesn't just depend on the video... the audio is important too. Don't ruin your audio quality by skimping on some bits for a probably near imperceivable improvement in video quality!

Regards.

[offline]

I know of quite of few people who have moved a PC into the living room, and use the video out's on their video cards, projectors, etc, to bypass all the restrictions built into a standalone.

Excellent point. Making an HTPC (Home Theatre PC) is the only
way to go if you want 100% playability of all formats. While you
can spend a small fortune on quiet HDD's, fans, insulated boxes etc.
one solution can be to network a laptop with video out to your mainbox
and use the resources of your main pc - there are also infra red and
radio signal transmitters (including pc remote control) which you can
get for less $$$ than it costs for a dedicated HTPC.

[postul8or]

Yes I think that is the way to go, have a PC with and output to your TV... As you say, just have a box or laptop to launch the media file over a network or something so that you don't have to listen to the fan and hard drive noise as much.

I just don't think that DVD players will come out with a firmware package flexible enough to play the new and improved codecs that come up all the time.

[sterno]

For something like a home-theater PC, the ultra-compact PCs like the one Shuttle sells are very appealing. Tom's Hardware reviewed one a while back, it used some kind of "heat pipe" cooling system to minimize the need for fans. Combine that with a 5400RPM drive (or possibly even a notebook drive with an adapter), and it would be virtually silent. These PCs also tend to be cheaper than notebooks (partly because they don't have an LCD).