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.wav vs 328K MP3?

R

Robert Bass

I work for a non-comm station that implemented hard-drive audio in 2002. Our server contains a 73 GB drive, and at the suggestion of the company that sold us the system, we rip everything to 328K MP3’s.

We are hoping to go HD within a few years, and I’ve only recently stumbled across cautions that suggest no MP3’s should be used for the HD signal. Does this mean we need to re rip everything as .wav files, or is 328K high enough in audio quality that it won't make a major difference?

My primary reason for asking is because of the hard-drive size. Lately we’ve been running into situations of maxed out drive space and have had to delete old files. I’m trying to persuade them to expand the server, but that’s been met with hesitation. It’s probably a financial situation.

I figure if we’ve got to change over to .wav format, then it’s just about going to force the issue of server expansion. We might as well get that out of the way before firing up the HD signal for the first time. :)

R
 
Would you mind posting a link to the Hillary Clinton quote in your sig?
 
Digitization Options

Getting back to the original topic...

The problem with 328K MP3 isn't the bit-rate, it's the fact that it's a lossy compression scheme. That means that some bits of information are going to be lost. When you go to HD, you have different compression schemes used in the audio chain that will emphasize the loss of bits, reducing the quality of the music.

The .wav format doesn't lose any bits. You can adjust the sampling rate and quantization to reduce file sizes. Sampling rate will affect the maximum frequency that can be reproduced. The rule is that you need minimum of two samples to reproduce a frequency correctly, so the typical CD sampling rate of 44,100 samples per second can represent a maximum frequency of 22,050 Hz. Obviously, that's a lot more frequency range than is necessary for AM radio, and more than minimal for FM radio. If you reduce your sampling rate to 32K samples/sec., you'd max the audio at 16KHz. That may be enough for broadcast. Let me state here, however, that the higher sampling rate will give you cleaner-sounding samples at ALL frequencies below the max, which is why the CD standard became 44.1K in the first place.

Quantization (8-bit, 16-bit, 24-bit, 32-bit) is the number of levels of amplitude available to reproduce sounds. For example, on an audio wave form, the Y-axis represents amplitude, or loudness. If you use an 8-bit sample, you have 256 different volume levels available for each sample - +128 and -128. With 16-bit quantization, you have 65,536 levels of volume available. With 24-bit quantization, you have over 16-million. Anything over 16-bit is probably overkill.

Lastly, hard drive space is cheap. If you have an older server, using mirrored SCSI drives, they're quite expensive to replace or upgrade. Check to see if your server has an unused EIDE interface, or a free PCI slot, and consider installing EIDE drives as new volumes for music storage. GOOD 250GB drives are around $100.00 each. Get two, and either mirror them, or use one as the primary drive and the second as a backup.

BTW, you could also plug in one or more external hard drives, but my experience has been that external drives don't last as long as internals (cooling issues), and the rate of data transfer from the external drive to the system isn't as fast as I'd like.
 
You can get 500GB SATA drives for $130.00 from newegg... Start ripping uncompressed, and repace the MP3s as time allows, hopefully you'll have weeded it all out before turning on the HD. Buy a PCI SATA (RAID, if you wish) card to interface the new drive to your automation server. I agree w/ SirRoxalot that MP3 does not process well through the iBiquity codec (or a compressed STL for that matter), though I personally cannot detect a difference between linear audio and 320kB MP3 in the analog domain.

I'd recommend not using EIDE drives for audio storage on an older PC/servers on-board IDE interface. The automation manufacturers used SCSI drives for the increased bandwith (now a moot point with SATA). If you're using a windows based system, remember to format the drive with the largest block size possible.
 
Several years ago we started the "music process" on heading to HD. We used to be compressed on the central server and now we are using .WAV. Everything for the past two years has been ripped as .WAV and on the older stuff we used a "Batch" conversion program to convert them to .WAV as well. We are now redubing the older stuff that was converted because even though they are all in the .WAV format, they still have bits missing because they were converted from a compressed format. 1TB server, mirrored, EIDE.
 
Out for a Drive

EIDE - even DMA33 - has plenty of bandwith to provide music on demand to multiple radio station simultaneously. Typically, the server is only providing data to one studio computer at a time, and not necessarily in real time. Even providing real-time music to 3 or 4 radio stations isn't going to max out the data path of the hard drive interface.

There are problems with older technologly, however. Old servers - circa 2001 or 2002 - may not support current hard drives, and may especially have problems with drives larger than 137GB. There are workarounds, but an ATA/133 controller or SATA controller plugged into a PCI slot is a better way to assure support for large hard drives and higher data rates. The purpose of SCSI in the first place was better bandwidth, and support for larger drives, but the price is crazy compared to EIDE or SATA drives.

There are some inexpensive SATA drive mirroring controllers, and SATA drives are competitive with EIDE drives in price. The data transfer rate is considerably higher. Bottom line is that if you have to buy a new hard drive interface card for your old server anyway, you might as well get an SATA mirroring controller and have your music info backed up instantly and automatically.

Remember, however, that mirroring drives doesn't guaranty that you have a backup. There are many types of failures that will take out the mirroring controller and all local hard drives, leaving you with no music data. Backups to a different machine and/or different removable medium are a must for full protection.
 
Robert Bass said:
I work for a non-comm station that implemented hard-drive audio in 2002. Our server contains a 73 GB drive, and at the suggestion of the company that sold us the system, we rip everything to 328K MP3’s.

We are hoping to go HD within a few years, and I’ve only recently stumbled across cautions that suggest no MP3’s should be used for the HD signal. Does this mean we need to re rip everything as .wav files, or is 328K high enough in audio quality that it won't make a major difference?

My primary reason for asking is because of the hard-drive size. Lately we’ve been running into situations of maxed out drive space and have had to delete old files. I’m trying to persuade them to expand the server, but that’s been met with hesitation. It’s probably a financial situation.

I figure if we’ve got to change over to .wav format, then it’s just about going to force the issue of server expansion. We might as well get that out of the way before firing up the HD signal for the first time. :)

R
Click to expand...

I recall in early HD discussions, the need for a 44.1K sampling throughout the system was needed for best performance and integration. Of course once the encoder gets ahold of it, bye bye uncompressed audio but you dont want to compress audio already compressed anyway! (UGH)....Personally, I would go WAV format on everything..
HDs are cheap nowadays.....When I installed my 1st Prophet system, I did a A-B test on the air of a song we had on CD...the MPEG2 4.4:1 had less low end and the mid range sounded a little less..When NexGen came out, I saw where they offered uncompressed audio even though it defaults to MPEG2....but the AudioVault system is replaced was WAV (gawd I wish I could have copied the drives before the AV was shipped off to another station!)

IMHO, I would start looking at increasing or replacing the server drives (or server) and have a backup (SNAP drive or just another PC with tons of IDE drives in it...dont need fast speed in the back up...just a place to keep the files safe)
DAT tape would be another possibility (OR gasp, CDs and CD machines to play them on the air...at least as a non-comm you dont have to worry about loss of commercials! :)
 
Is the Hillary Clinton quote something she actually said, or was it made up to try to amuse someone?
 
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