How to fix Audio problem with vcd authoring

[thelotusman]

Hi there, I have a very frustrating problem and I'm hoping someone can help me. Firstly a bit of background, my friend recently poste a question about my jukebox and the vcd's I have been attempting to author for it. You guys were great, replying on mass and in great detail and as a result I was able to fix half the problem. I have sucessfully been able to transfer mpeg 1 video tracks from ARES.com onto blank cd's that now play in my Jukebox as VCD,s.

Heres the problem.... The picture on all these files seems fine but on at least every second track I download the audio is very jumpy. When I say jumpy I mean you can hear glitches and it literally sounds like when you hit a bump in your car with a cd playing. Now it doesnt do this on every track I download. For example Artist : Moby with song title : 'Why does my heart feel so bad' plays perfectly and does not jump and picture is perfect whereas Artist : Bruce Hornsby with song title 'Thats just the way it is' is jumpy as anything. I know the type of file that they re because I have a program to convert all the files to mpeg1. I spoke to the guy who I bought the jukebox from and he seemed to know a little about this. You see all the copywrite vcds I got with the machine play perfectly, its just some of the ones I burn that are jumpy. He says its something to do with the ALC (automatic level control). He says that all the copywrite vcds have been recorded at around -10 decibell and that the jukebox does not like tracks that are less than -5 decibell but -10 decibell is best for it. He says that tracks that are 0 decibell or higher will jump as the optics in the jukebox have trouble playing them correctly. This all sounds fair to me but can someone give me a second opinion. He says that the reason that some tracks play and some dont is because obviously the ones that do play are recorded with an alc of between -5 and -10 decibelss and the ones that dont play are obviously higher. Does this sound right and if so is there any way that I can convert all the tracks to be between the required -5 to -10 decibells an if so what program can Iget to do this. I have been using the latest NERO but there does not seem to be a provision to change the ALC (Decibells). That is if the ALC can even been changed on these tracks once downloaded from sites such as ARES (Can they?).

SORRY THIS IS SO LONG WINDED BUT I REALLY NEEDED TO EXPLAIN THE PROBLEM FULLY. TO ALL THOSE WHO GAVE THE GREAT REPLIES INITIALLY THANKYOU SO MUCH I WOULD HAVE BEEN LOST OTHERWISE. I WOULD BE OVER THE MOON IF SOMEONE COULD HELP ME WITH THIS PROBLEM AS SOME OF MY FAVORITE TRACKS CANT BE PLAYED ON MY MACHINE AT THE MOMENT BECAUSE OF THE PROBLEM. THANKS A MILLION YOU GUYS YOU HAVE BEEN GREAT.

REGARDS ELLIOTT

[guns1inger]

From what I cam make out, this software is basically just a commercial p2p program that downloads video and audio in the same way as any other p2p program. But asks you to pay up front for the privilege of getting something most other people download for free.

If this is the case, and putting the legalities of the likely content to one side for the moment (and for the mods to sort out), then quality of the content is going to be variable, to say the least. P2p is littered with poorly encoded crap, created by people with little skill and a pirate copy of WinAVI. If you want quality source then you have to go and buy it, not download it from dubious places.

[thelotusman]

Hi thaks for the reply but I dont believe this is the problem. I have down loaded the clips from numerous sites (by the way Ares is free) aside from ares including limewire and bitlord and the problem is the same with specific clips only. When you look at the individual qualities of each file they are much the same between clips that work and clips that dont work. As i mentioned the guy I bought the machine from is adament the problem has to do with ALC, he just doesnt know of a program that can adjust this as you download prospective clips off these sites. He knows it can be done but doest know the program that does it. thanks for taking the time to reply. Furthermore, believe it or not the original VCDs that were supplied with the jukebox contain tracks downloaded legally from the net, they are the same files, obviously these anufacturers were able to govern the ALC to a - decibell reading I presume?

Regards Elliott

[Abond]

Analyse the clips with GSpot. Look for the difference...

[guns1inger]

Two video clips. Both Xvid video and mp3 audio. One is encoded by someone with WinAVI and no idea, then other is encoded with virtualdub by someone who knows what they are doing. G-spot will show them both to be basically the same, but the actual quality will vary markedly. In my experience, anything to do with Limewire sits squarely in the WinAVI/No Idea camp.

[jman98]

Besweet can probably fix your audio problems, but you'll have to demux everything first and then re-author the VCDs. Get Besweet GUI, which is a little easier to use than command line Besweet.

Have you ever stopped to consider that maybe it's just not worth it to play VCDs on this piece of #$%@ VCD player that you have? I would seriously just buy a DVD player that supports VCD and be done with it, but I never cease to find people in the video world who place no value at all on their spare time and will gladly spend many painful hours converting various video files just so they'll play in some old, obsolete system rather than spend $50 or so dollars (US money) just buying a new and better DVD player. VCD is pretty ancient technology by today's standards. Is it REALLY worth what you are having to do to make this work? I remember in the earlier part of the decade when there were people who would spend at least 4 hours on weekends doing painful DVD to VCD/SVCD conversions back when DVD burners were incredibly expensive. At some point I'd think that the spare time would worth more than saving the $20 it would cost to just by the film on DVD, but that's just me.

[Cornucopia]

Legalities aside, if you want to troubleshoot this correctly, you need to see which stage this becomes a problem.

Let me say up front that your "technical source" is fishing for an answer. A VCD player works this way:

• VCD encoded disc is read by laser
  Decoder circuit strips out and compares error-correction/error-detection code
  Decoder circuit unscrambles user data
  Buffer pieces together packets into seamless mpeg stream
  MPEG decoder parses and splits to MPEG video decoder and MPEG audio decoder
  MPEG video decoder returns video to regular uncompressed 1/4 D1 stream, while MPEG audio decoder returns audio to regular LPCM stereo stream
  Video processor upconverts 1/4 D1 stream to full screen (D1) size
  (If analog needed) Video and Audio D-to-A converters spit out Analog versions
  It arrives at output jack to be connected to Monitor and Amp/Speakers

The ONLY place in this chain where one even gets to "level control" is near the end when going from MPEG audio to LPCM audio and when going from Digital to analog (and at the amp when amplifying it). MPEG audio decoders are BUILT to decode within the full spectrum of level possibilities (aka full 0dB-to- -96dB) or better. Decoders like this also CAN'T output an "illegal" stream (one that is, say "over-modulated" or "above 0dB). As long as it is <0dB, the next link in the chain--the D-to-A--shouldn't have any trouble with it either. While there might be some factory miscalibration, usually it either WORKS or DOESN'T WORK. At all.

Things such as burned vs. pressed might affect things like the buffer memory (skipping because of mis-reads, etc), but this will affect video as well as audio (because at this stage they're intertwined).

Do ALL of your downloaded clips sound OK (BEFORE converting to MPEG1)?
Do ALL of your MPEG1 clips sound OK in MediaPlayer, etc (BEFORE authoring/burning to VCD)?

Realize that LOTS of audio programs can provide a gain adjustment (which is what you're talking about) or more specifically, normalize to some arbitrary maximum (whether 0bB or less than). Audacity, Goldwave, CoolEdit/Audition, ProTools, Soundforge, even smaller utilities and command-line apps.
But, if you've got skipping/hiccuping, this ISN'T a result of level. If that were a problem, you'd be hearing overload distortion at those points instead.

BTW, you actually DON'T want true ALC (auto level control). This is a constant audio level compression activity which would result in "pumping" noise.

Scott