[57]

In an OTA thread yesterday, several people brought up this issue. Those posts were deleted since they hijacked an OTA thread.

I'd like to start that "debate" again here. (the people who were discussing digital vs analogue cameras in that thread may do the same in a new thread)

If I recall the gist of what people were saying, they were stating that MP3s were better than CDs because 128 is higher than 44.

I believe people have got bitrate and sampling frequency mixed up...

 

[JohnnyG]

Yup, that's mixed up all right! The sampling frequency of CD is 44.1KHz. That means that the audio waveform is sampled 44,100 times per second. Each sample is captured with 16 bit accuracy. Simple math will show you that the bit rate of CD is therefore approximately 705kb/s. That's the number to compare to an MP3 at 128kb/s.

When an MP3 is uncompressed, it's output once again matches the specs of CD.

 

[mrhooie]

mp3 quality, I find, varies on the bitrate and how many times it's been downladed, transfered or 'whored out'

I've had a few 320kps mp3s that were passed around a few times still exhibit a digital "hiss" as I'll call it. not noticeable 100% of the time or through cheap headphones. But definitly noticeable on my home stereo and computer headphones

 

[JohnnyG]

If you're playing the files back on your PC, then it's almost certainly your PC's sound card that's responsible for the hiss. The audio output on my Dell notebook, for example, is just aweful.

 

[MarcP]

and how many times it's been downladed, transfered or 'whored out'

Then you have a serious file integrity problem. Your statement should be false if your harddrive or network connection is healthy. Imagine a Word document losing letters as you pass it around. Unacceptable. Files do not degrade by being downloaded or transferred. They don't wear out.

 

[ken0042]

When I used to sell electronics; it was right when MP3's were becoming popular. (Late 90's). I had other salespeople make mixed CD's from MP3's. Playing them on the cheap systems were fine; but when the time came to show off $2000-$3000 per pair speakers; you could hear the difference.

I also swore I could hear the difference between a burned CD and a stamped one too. With speakers being high commission; it was worth it to have a good quality stamped CD in your pocket. Yeah, I had a few get wrecked or lost. But it was worth it.

 

[filper]

Wait until the 'fileswap' generation enters the workforce, buys their first 'bigass' stereos, and starts playing thier 'old' mp3 burn CD's on a real machine...

 

[GQUEUE]

Correct me if I am wrong, but isn't MP3 a lossy compression, so regardless of the bitrate or sampling rate, you are going to lose something on the overall sound. In other words, if you have a pure analog signal coming in and you digitize it, you essentially get a digital representation which can then be encoded into a particular format (like a .WAV file for example). If the encoding is lossless, then the digital representation can be exactly reproduced (like a CD). If the encoding is lossy (like an MP3), the resulting decoded digital representation is similar, but not exactly like the original digital representation. When either of these digital signals gets converted back to analog, it is similar to (but not exactly like) the original analog signal. But arguably, the lossless representation will be closer to the original because it has more of the original information content (ie. the CD should be better than the MP3).

The point I had made in the previous thread (and I take responsibility for taking it OT, I am sorry) is that while MP3's are not necessarily as high quality as CD's (by the above argument) they are appealing because their small file size makes it possible to do more with them and the sound quality is good enough for most purposes. The ultimate point here is that quality is not necessarily the end all criterion for a lot of people.

Can you make a high quality MP3 that is as good/better than a CD? Sure. But it will be larger in size than most of your 'typical' MP3s that you see, because you can't get something from nothing.

 

[filper]

MP3's are as effective as photocopying the Mona Lisa.

 

[JohnnyG]

GQUEUE, it's like HD on a 12" TV. Sure it can be done, but you aren't going to see a difference, so it's overkill. A super compressed NTSC video signal will likely look just as good.

As it is with CD audio, or DVD-A or SACD....the difference will only be appreciable on reproduction equipment above a certain quality level.

 

[Arthur Dent]

Wait until the 'fileswap' generation enters the workforce, buys their first 'bigass' stereos, and starts playing thier 'old' mp3 burn CD's on a real machine...

I also hoped so, but from what I'm observing, they are more likely to by a boombox for their iPod, than a "bigass" stereo system. This generation is completely hopeless, most of them will never hear even CD quality music

 

[GQUEUE]

...it's like HD on a 12" TV. Sure it can be done, but you aren't going to see a difference, so it's overkill. A super compressed NTSC video signal will likely look just as good.

I agree....that's my point, the difference is unappreciable by most people. But, I think everyone here has known people who need to think they are buying the best in quality, regardless of whether they can see the difference or not. Its for people like this that the whole 'digital' marketing campaigns that you see are geared towards.

 

[JesseJ]

Does everyone forget what forum we're on, yet again? Many of the iPodders really don't care about sound integrity or quality. Buying expensive sound equipment in order to reproduce the sound, be it CD, SACD or DVD-A isn't what interestes these people. It's being able to get 5000 songs on a handheld machine so they can listen to what they want when they want.

I play MP3's on my 'bigass' stereo all the time, and don't really care. I can get 4000 songs on a DVD-R, and that's all I really care about.

 

[bgclarke]

When I rip CDs to put on my Creative Muvo TX to listen to on the bus, I rip them at 192/44. It's good enough for what I use it for.

I've played some on my stereo (using my DVD player) and they sound OK to me, but my ears are really messed up thanks to an Iron Maiden convert 20 years ago

 

[filper]

MP3's are ideal for portables and PC speakers, the file's 'underwater' compression anomalies just become more evident as the quality of the playback equipment increases.

I have a real problem with 128 bitrate even on portables.

 

[BHoward]

I think we should get some of the facts straight first ....

A CD song is as JohnnyG described ..... An Analog to Digial conversion sampled at 44.1Khz with a depth of 16 bits. This is then encoded onto a CD as basically a .WAV file. There is NO compression applied to the data (that is all it really is at this point). If the CD is made from a digital recording, then it will be resampled to the CD standard.

A LOSSLESS encoder will that this data and compress it so that the orginal data can be retrieved WITHOUT any data loss. Usually you will save about 1/2 the space. This is exactly the same way WinZip works. Some examples are APE, WMA, etc

A LOSSY encoder will compress the data but when expanded MAY NOT be the same as the original. Many factors play in when using this type of compression ie bit rate, file size, etc. Examples of these are MP3, MEG-2, JPEG, MPEG-4, WMA, etc. The intelligence of the encoder also plays an inprotant role in this ie the Lame encoder is renowed for it encoding ability.

Once a file gets encodered, downloading the file, copying the file, e-mailing the file will never change the original quality of the recording. Re-encoding may introduce errors on top of errors which may futher reduce the quality. For example, encode a WAV file to 320 VBR MP3 will sound every bit as good as the orginal but be 1/3 the size. Then encode this to 128bit for a music player. This file will not be as good as encoding from WAV to 128 bit. Why?? We are resampling the resampled 320bit which already has errors.

For myself, I use 320 Variable Bit Rate MP3 encoded with the Lame encoder. I cannot tell the difference between it and the orginal on my system. For portable MP3 players, I re-encode to 96 bit from my 320 VBR encoding.

 

[stampeder]

Yup, that's mixed up all right! The sampling frequency of CD is 44.1KHz. That means that the audio waveform is sampled 44,100 times per second. Each sample is captured with 16 bit accuracy. Simple math will show you that the bit rate of CD is therefore approximately 705kb/s. That's the number to compare to an MP3 at 128kb/s.

When an MP3 is uncompressed, it's output once again matches the specs of CD.

Thanks for that! Does anyone know if MP3s can do multi-channel too, such as on an SACD?

 

[JohnnyG]

When an MP3 is uncompressed, it's output once again matches the specs of CD.

Just so we're clear, this is technically correct in that the output is 44.1kHz/16-bit, but it should be noted that the samples themselves are not the same as the original.

A LOSSY encoder will compress the data but when expanded MAY NOT be the same as the original.

WILL NOT be the same, but you may not be able to perceive the difference.

 

[GQUEUE]

I think we should get some of the facts straight first ........Usually you will save about 1/2 the space. This is exactly the same way WinZip works...... I use 320 Variable Bit Rate MP3 encoded with the Lame encoder. I cannot tell the difference between it and the orginal on my system. .....

Well, if we're gonna get facts straight, then I don't think the 2:1 compression ratio applies to what we are discussing. Try compressing a music WAV file down with WINZIP. I think it is unlikely you will see a 50% reduction. The classic 2:1 ratio that everyone uses is given that the average data entropy across all different types of files (text, database, executables, etc...). Depending on the type of data and its content, the actual compression ratio can be much different. A great example of this are computer tape drives which have a 20GB native capacity and 40GB compressed. Unless you are only backing up word documents, it is very unlikely you will get 40GB on one tape.

When talking about a digital audio file, the amount of lossless compression is based on the entropy (or repetiveness if you will) of the digital data (ie. numbers). And the data could be highly compressible, but more likely will not be very compressible at all.

With regards to your last sentence, this hits the nail on the head. Its up to the listener to decide what is best. IE. if you could encode the MP3's at 64VBR and not tell the difference, then that's what you would use, even though you know there is a loss in quality.

It should also be mentioned that the quality of D/A conversion can play a huge role in all of this. I don't know if such a thing exists, but I wonder if anyone has ever done a study comparing an analog signal, its digital representation converted to analog and then the resulting analog signal from an MP3 encoded version. It would be interesting to see what the actual error % is between the original, the digital version, and the MP3 version.

 

[57]

I use Apple iTunes and it has a lossless encoder. Saves about 50%.

You are correct that some files do compress more than others on computers, programmes hardly compress, while you can get a 10:1 compression on some files.