Message 306063 - Python tracker

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Author	MosesofEgypt
Recipients	MosesofEgypt
Date	2017-11-10.23:40:07
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1510357207.47.0.213398074469.issue32004@psf.upfronthosting.co.za>
In-reply-to

Content
--- Issue --- audioop.adpcm2lin and audioop.lin2adpcm currently treat the high 4 bits of each byte as the first code and the low 4 as the second code. In practice this is often the opposite. http://www.drdobbs.com/database/algorithm-alley/184410326 https://wiki.multimedia.cx/index.php/Microsoft_IMA_ADPCM --- Steps to reproduce --- Run the attached script to decompress the attached wav to two different 16bit signed pcm wav files. The "GOOD" one had the nibbles of each code swapped before being decoded, while the "BAD" one didnt. --- Suggested fix --- I propose an additional optional boolean parameter to these functions to specify which nibble is the first code and which is the second. NOTE: I haven't compiled my changes to test as I do not know how to set up a cpython build environment. This commit is more intended to show how to implement the fix. https://github.com/MosesofEgypt/cpython/commit/4a5ca65833ec79857f065546ae0d90661ce26f5f

--- Issue ---
audioop.adpcm2lin and audioop.lin2adpcm currently treat the high 4 bits of each byte as the first code and the low 4 as the second code. In practice this is often the opposite.
http://www.drdobbs.com/database/algorithm-alley/184410326
https://wiki.multimedia.cx/index.php/Microsoft_IMA_ADPCM

--- Steps to reproduce ---
Run the attached script to decompress the attached wav to two different 16bit signed pcm wav files. The "GOOD" one had the nibbles of each code swapped before being decoded, while the "BAD" one didnt.

--- Suggested fix ---
I propose an additional optional boolean parameter to these functions to specify which nibble is the first code and which is the second.

NOTE: I haven't compiled my changes to test as I do not know how to set up a cpython build environment. This commit is more intended to show how to implement the fix.
https://github.com/MosesofEgypt/cpython/commit/4a5ca65833ec79857f065546ae0d90661ce26f5f

History
Date	User	Action	Args
2017-11-10 23:40:07	MosesofEgypt	set	recipients: + MosesofEgypt
2017-11-10 23:40:07	MosesofEgypt	set	messageid: <1510357207.47.0.213398074469.issue32004@psf.upfronthosting.co.za>
2017-11-10 23:40:07	MosesofEgypt	link	issue32004 messages
2017-11-10 23:40:07	MosesofEgypt	create