New WMA Audio Codecs

This project is part of the Google Summer of Code 2010 project.

Project name	Student	Mentor	Backup mentor
New WMA Audio Codecs	Mohamed Tarek (mt)	Michael Giacomelli (saratoga)	Dave Chapman (linuxstb)

Rockbox already contains an ASF parser and a decoder for the WMA standard codec. The primary goal for this project is to add support for the WMA Professional codec, and then if there were still time, WMA Voice codec.

Relevant resources

• Information about the different WMA codecs :
  
  • Wikipedia : http://en.wikipedia.org/wiki/Windows_Media_Audio
  • Microsoft : http://www.microsoft.com/windows/windowsmedia/forpros/codecs/audio.aspx
• ffmpeg r22886 : http://git.ffmpeg.org/?p=ffmpeg;a=tree;h=8035401d5c80ffe90e19a50b5f56aa78600f51d7;hb=85f93f1070703b31bb8ae35ed0b7b99943e52646
• Task on FlySpray : FS#11281

Project plan

• Factor out the ASF-specific code from apps/codecs/wma.c and apps/codecs/libwma to create an independent ASF parsing library.

• For both codecs, the plan would roughly proceed from here as follows :

  • Extract the codec files from ffmpeg and make them compile standalone.
  • Modify the ASF parser if needed to support the new codec.
  • Write a .codec file and get the taget audio streams working in the sim.
  • Modify the codec's files to use fixed-point arithmetic instead of floating-point.
  • Test and debug on target.

Currently working on

• Removing dead/unneeded code.

Current Status

• Codec plays and seeks.
• Works on targets with codec buffer > 550KB
• Decodes in 151% real-time using a 320kbps test sample on sansa e200.

Progress

Date	Achievement	Code in SVN
Fri, 30 Apr	Extracted the necessary files for WMA Pro from ffmpeg r22886 and copied them to apps/codecs/libwmapro.	r25763
Fri, 30 Apr	Applied a minimal set of modifications to the files in libwmapro to make them compile standalone. See libwmapro/README.rockbox.	r25764
Sun, 2 May	Factored out the ASF-specific code from apps/codecs/wma.c, created an independent ASF packet-handling library, and applied the necessary changes to use that library in the ASF metadata parser and the current wma codec.	r25780 r25783
Mon, 10 May	Modified the ASF metadata parser to work with wma pro streams. ASF packets seem to be independent of the codec type, so no modifications were done on the packet-handling functions.	r25922
Mon, 21 June	Wrote apps/codecs/wmapro.c and modified libwmapro to make the codec work in the sim. (For compiling see README.rockbox)	r27006
Mon, 5 July	Partial conversion of the WMA Pro decoder to fixed point arithmetic. Currently inverse quantization & rescaling, imdct and windowing are all in fixed point.	r27302m
Mon, 12 July	Complete conversion of WMA Pro to fixed point arithmetic.	r27402
Wed, 14 July	Removal of the floating point code from apps/codecs/wmaprodec.c, and some additional modifications to make it compile on target, with Rafaël Carré (funman) doing some bug squashing in revisions r27419 to 27423 (Thanks!)	r27416 r27417

-- MohamedTarek - 2010-05-02