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Topic: how to change mp3 header information programatically? (Read 4655 times) previous topic - next topic
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how to change mp3 header information programatically?

hi,

I am just downloading one mp3 file from server.i want that the mp3 song should be played by only my application.

I have tried the below__
1.DES encryption,but it takes time to decrypt the file  before playing.

2.xor ,but it writes only one by one byte so it takes too much time.

so my question is_

is there anyway that i can make mp3 file non readable by other sources except my application without westing time prior to playing.?

is there anyway that if i can change some header or id3 tag information so it cant be played?


regards,
hitendrasinh gohil

how to change mp3 header information programatically?

Reply #1 –
XOR'ing an mp3 file takes maybe a couple milliseconds.  Just fold that into your decoder.

how to change mp3 header information programatically?

Reply #2 –
Quote from: saratoga on
XOR'ing an mp3 file takes maybe a couple milliseconds.  Just fold that into your decoder.


i have tried that but doing xor'ing we need to write a file byte by byte and it takes a too much time.i need something that takes a fraction of time to play mp3 song.

 

how to change mp3 header information programatically?

Reply #3 –
Quote from: hitendrasinh on
Quote from: saratoga on
XOR'ing an mp3 file takes maybe a couple milliseconds.  Just fold that into your decoder.


i have tried that but doing xor'ing we need to write a file byte by byte and it takes a too much time.i need something that takes a fraction of time to play mp3 song.


Two problems that I can see:

1)  The XOR instruction on x86 is 4 bytes wide (or 16 bytes with SSE).  If you XOR each value 4 (or 16) times, and throw away 3 (or 15) of them, then yes thats going to be slow.  I recommend just XORing each thing one time and not throwing away any of the results.

2)  Writing to disk is slow.  Don't do it.  Load the first mp3 frames into memory, XOR them, and then decode them.  If the process gets measurably slower, you have made a mistake somewhere.  This should literally take so little time you cannot measure it.