iPod Users break free
Moderator: Jedi
Re: iPod Users break free
Calling CDs compressed implies that some form of compression algorihm has been employed to master CDs and that conversley, some form of decompression would be required to playback the data on CDs. This is simply not the case. The audio data stored on CDs is 2 channel 16 bit PCM sampled @ 44.1khz. The data stream is uncompressed. This is totally different to lossey compressed digital formats such as MP3.
Re: iPod Users break free
You need an algorithm for downsampling. On the simplest level the algorithm has to take two adjacent samples and produce one new one by averaging the information from the two. In effect you lose ALL you original data and produce a new data set that is 50% the size of the starting file.
Good algorithms will of course average across more than two samples. But the effect is the same.
Therefore it is not only 100% lossy, but irreversible if you don't save your original file. It's the same as reducing the number of pixels in a tiff image. You have to do this to your original wav file if you didn't record it at 44.1kHz. Which you won't have done since better result in terms of audio editing (which includes an audio version of compression, noise reduction, etc) if you edit with high sample rates and then downsample.
With bit depth compression you are essentially delete all the memory addresses which carry no value as a first step then average similar values through time (or space for pictures or space and time for video) as the second step. TIFF to jpeg and Wav to MP3 are bit depth compression, although you can include pixel number or sample rate if you want.
Good algorithms will of course average across more than two samples. But the effect is the same.
Therefore it is not only 100% lossy, but irreversible if you don't save your original file. It's the same as reducing the number of pixels in a tiff image. You have to do this to your original wav file if you didn't record it at 44.1kHz. Which you won't have done since better result in terms of audio editing (which includes an audio version of compression, noise reduction, etc) if you edit with high sample rates and then downsample.
With bit depth compression you are essentially delete all the memory addresses which carry no value as a first step then average similar values through time (or space for pictures or space and time for video) as the second step. TIFF to jpeg and Wav to MP3 are bit depth compression, although you can include pixel number or sample rate if you want.
Re: iPod Users break free
That doesn't change the fact that the data stored on CDs is not compressed and therefore your original assertion that CDs are compressed is false.
You should have said "the audio data stored on CDs generally has a lower sample rate than its original source and therefore could be considered 'compressed' when compared to its original source." Saying "CDs are compressed" isn't the same thing.
You should have said "the audio data stored on CDs generally has a lower sample rate than its original source and therefore could be considered 'compressed' when compared to its original source." Saying "CDs are compressed" isn't the same thing.
Re: iPod Users break free
It's a relative term. The original assertion that CDs are uncompressed is equally at fault.
Nobody suggested we were discussing bitrate compression rather than resolution compression.
Nobody suggested we were discussing bitrate compression rather than resolution compression.
Re: iPod Users break free
What original assertion?Burbage wrote:It's a relative term. The original assertion that CDs are uncompressed is equally at fault.
Re: iPod Users break free
This one.Bender wrote:No they're not.Burbage wrote:CDs are compressed.