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Topic: conformance testing of bitstreams (Read 4785 times) previous topic - next topic
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conformance testing of bitstreams

Im learing proper conformance testing of mp3 bitstream playback - can someone go over the process that is used - giving step by step for a newbie?

What tests should be run?  How do you verify the results?  etc....or where do I find the info out about how to properly do this?

regards

barbe

conformance testing of bitstreams

Reply #1 –
Quote
Im learing proper conformance testing of mp3 bitstream playback - can someone go over the process that is used - giving step by step for a newbie?

What tests should be run?  How do you verify the results?  etc....or where do I find the info out about how to properly do this?

regards

barbe
[{POST_SNAPBACK}][/a]

Read this: [a href="http://www.underbit.com/resources/mpeg/audio/compliance/]http://www.underbit.com/resources/mpeg/audio/compliance/[/url]

Official spec for conformance testing:
ISO/IEC 11172-4:1995
ISO/IEC 13818-4:1998

conformance testing of bitstreams

Reply #2 –
Ah thanks - I was already looking at that document and the other refs from ISO -- but what Im really looking for is perhaps some test tools or scripts?

Once I get the raw audio file output from the decoder - what do I do to compare it against the refrence file?

Must I write a script that goes thru and does a difference signal between the two files (original - decoder output) -- then compile that data and do an RMS on the output file?  OR is there a tool that is already out there for people to use?  Im sure this must have been done by others....but I cant seem to find anything on it.

Also - I have seen refrences to MD5 comparisons used in other testing guides (Phillips) -- is this an alternative way of checking??  I thought MD5 meant bit exact -- so this test mentioned with difference signals implies to me that they will NOT be bit exact....

Sorry Im still a bit confused....(newbie blush)

Barbe


Quote
Quote
Im learing proper conformance testing of mp3 bitstream playback - can someone go over the process that is used - giving step by step for a newbie?

What tests should be run?  How do you verify the results?  etc....or where do I find the info out about how to properly do this?

regards

barbe
[{POST_SNAPBACK}][/a]

Read this: [a href="http://www.underbit.com/resources/mpeg/audio/compliance/]http://www.underbit.com/resources/mpeg/audio/compliance/[/url]

Official spec for conformance testing:
ISO/IEC 11172-4:1995
ISO/IEC 13818-4:1998
[a href="index.php?act=findpost&pid=352006"][{POST_SNAPBACK}][/a]

conformance testing of bitstreams

Reply #3 –
Hi,

  If you have understood what are the cirteria for the conformance test then it is easier to do the testing. you have to check the RMS diff & Absolute diff.  the former one is more important.

  For calculating the RMS diff, the formula is RMS diff = sqrt(summation(sq(r-t))/n)
where t is i'th sample from decoder under test
& r is i'th sample from reference decoder.

  You must have the reference file & the file decoded by using your decoder.

  Then u can write a C program to calculate the RMS diff & Abs diff values.









Quote
Ah thanks - I was already looking at that document and the other refs from ISO -- but what Im really looking for is perhaps some test tools or scripts?

Once I get the raw audio file output from the decoder - what do I do to compare it against the refrence file?

Must I write a script that goes thru and does a difference signal between the two files (original - decoder output) -- then compile that data and do an RMS on the output file?  OR is there a tool that is already out there for people to use?  Im sure this must have been done by others....but I cant seem to find anything on it.

Also - I have seen refrences to MD5 comparisons used in other testing guides (Phillips) -- is this an alternative way of checking??  I thought MD5 meant bit exact -- so this test mentioned with difference signals implies to me that they will NOT be bit exact....

Sorry Im still a bit confused....(newbie blush)

Barbe


Quote
Quote
Im learing proper conformance testing of mp3 bitstream playback - can someone go over the process that is used - giving step by step for a newbie?

What tests should be run?  How do you verify the results?  etc....or where do I find the info out about how to properly do this?

regards

barbe
[{POST_SNAPBACK}][/a]

Read this: [a href="http://www.underbit.com/resources/mpeg/audio/compliance/]http://www.underbit.com/resources/mpeg/audio/compliance/[/url]

Official spec for conformance testing:
ISO/IEC 11172-4:1995
ISO/IEC 13818-4:1998
[a href="index.php?act=findpost&pid=352006"][{POST_SNAPBACK}][/a]

[a href="index.php?act=findpost&pid=352699"][{POST_SNAPBACK}][/a]

conformance testing of bitstreams

Reply #4 –
It seems that RMS level only suit for the supplied sine sweep (20Hz-10kHz) with an amplitude of -20dB relative to full scale. for example the test bitstream:compl.mpg,
but other bitstream is not the same, Must we calculate RMS for every bitstream and check whether RMS<2^-15/sqrt(12) ? I still fill confused.