Can downloaded files pick up jitter as they go through the Internet.

BlueFox

BlueFox

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It is already known that a music file can have jitter introduced into it as the bits are reconstructed due to slight timing errors in detecting where it transitions from a 0 to a 1, or from a 1 to a 0. This has me wondering if a downloaded file can suffer the same fate. The packet will undergo a number of transitions such as electrical to optical to electrical as it travels through the net. When it hits a router it will go from Ethernet to an internal format and back to Ethernet as it leaves the router. While the CRC will be correct it certainly seems possible jitter can be introduced into the file.


At least that is my current thinking, but I have no idea how to test it. Maybe if there were a way to get the HD file on a USB drive and compare it with test equipment (and listening) to the downloaded version that might be a method.

Any ideas? Does this make sense?
 
I always thought they just came corrupted in some way. One of many reasons I don't do downloaded music from anywhere. Perhaps this description is at least in part the reason why?
 
With the right downloading and transfer protocols, bit by bit acuracy of a file is actually warranted. But it also depends on the file format. WAV files for instance have no crc so unless transferred in specific ways (that are not normally used), the will get slightly, or not so slightly corrupted, at every use and transfer.

Also, a comparison to a CD is not necessarily conclusive, as they can have errors too.

Technically, that's no jitter because there is no timing in a file, but bits errors.
 
There are file compare programs that will test the file contents bit by bit and report differences. So you could use any file of reasonable length in any music format, up load it to, say, your Dropbox account, and download. Do this a number of times ending up with a file that has be subject to numerous transfers, then run the file transfer program.

Alternatively there are "check sum" programs that will examine a file and derive a lengthy code from its bit content. Then do the upload and down load thing as above, then run the check sum program and the resulting file. If there are differences, even tiny ones, the check sums won't be equal.

Free versions of file compare and check sum programs are available -- you guessed it -- for download.

Internet and inter-machine transfer protocols are very robust. Likely you will find know differences.
 
The problem is jitter will not change the CRC, or checksum. The bit for bit accuracy is still there, but the timing is now off. While jitter will not affect text data, it does affect musical data.
 
Hmm, I wonder if EAC (Exact Audio Copy) would be useful for this? (Yes, download for free from the interwebs).
 
I believe timing would only be relevant in the conversion done by your DAC, else, bit perfect is just that. In the digital domain, bits 'r bits. I don't believe your digital bits include timing info in any kind of sideband data, but I could be wrong on this. Still, it would be digitized and errors in transferring digital info is not tolerated, e.g. a massive Excel spreadsheet can't have one bit of data in a single cell suddenly be different as a result of file transfer. Your computer and the interwebs don't know if its an excel spreadsheet or a FLAC.
 
NorthStar said:
What are the experts saying?
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Does it matter what the so called experts are saying?

There is a right and wrong answer to this and the "expert" could say what he believes (usually lots of bias there) and an idiot could vomit back the correct answer that he read somewhere.
 
BlueFox said:
The problem is jitter will not change the CRC, or checksum. The bit for bit accuracy is still there, but the timing is now off. While jitter will not affect text data, it does affect musical data.
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No, you misunderstand jitter. Hate to say but ... bits are bits when it comes to file transfers. Jitter is a problem, yes, but jitter is introduced elsewhere than in the bit-perfect transfer of data files.

In S/PDIF or synchronous transmission the bits aren't the whole story because irregular timing of the arrival of the bits at the DAC can cause jitter, (depending on the exact technology and anti-jitter measures taken). However in the download of a file data over the Internet, or between computer A and computer B, or between disk 1 and disk2, jitter isn't introduced because the timing of the arrival of the bits is irrelevant. No jitter is caused and no jitter is stored on the transferred copy of the file.
 
Bobvin said:
I believe timing would only be relevant in the conversion done by your DAC, else, bit perfect is just that. In the digital domain, bits 'r bits. I don't believe your digital bits include timing info in any kind of sideband data, but I could be wrong on this. Still, it would be digitized and errors in transferring digital info is not tolerated, e.g. a massive Excel spreadsheet can't have one bit of data in a single cell suddenly be different as a result of file transfer. Your computer and the interwebs don't know if its an excel spreadsheet or a FLAC.
Click to expand...

Exactly. For any data file transmission bits are bits -- doesn't matter if the transfer is from one local disk to another or over the Internet; it doesn't matter whether the transfer is fast or slow or split into hundreds of pieces coming from different locations at different times (as it might be in bit torrent download). The rate -- or even the sequence -- of arrival of the constituent bits of a file is irrelevant to such a data transfer. Copy A of a file that is bit-identical to copy B is identical -- period.

DAC decoding is different from file transfer in that is that rate of arrival of bits IS relevant, and unless measures are take to assure the constant arrival of bits, jitter is introduced.
 
Julot said:
With the right downloading and transfer protocols, bit by bit accuracy of a file is actually warranted. But it also depends on ... the file format. WAV files for instance have no crc so unless transferred in specific ways (that are not normally used), the will get slightly, or not so slightly corrupted, at every use and transfer.

Also, a comparison to a CD is not necessarily conclusive, as they can have errors too.

Technically, that's no jitter because there is no timing in a file, but bits errors.
Click to expand...

...The DAC used?
 
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