Monkey's Audio

Overview

Monkey's Audio (also called APE or MAC) is a lossless compression format. The home page is http://www.monkeysaudio.com

Monkey's probably has the highest compression of all the lossless codecs, but it comes at a price - decoding is very CPU intensive, and not all compression levels are playable in realtime in Rockbox.

Monkey's audio has five compression modes, with each mode compressing to a smaller size, but significantly slower to decode than the previous one. -c2000 or -c3000 are a good compromise between compression size and decoding speed.

• -c1000 - "fast"
• -c2000 - "normal"
• -c3000 - "high"
• -c4000 - "extra high"
• -c5000 - "insane"

In addition, Monkey's Audio (currently at version 3.99) has been through many incompatible format changes in its life - most versions of the encoder produce files which are not decodable by earlier versions of the decoder.

Current Status

The Rockbox Monkey's Audio codec only supports v3.97 or later files.

Rockbox supports APEv2 tags in Monkey's Audio files, but does not read (or skip) id3v2 tags, which some applications also add to APE files. If a file has an id3v2 tag, it won't work in Rockbox.

Performance

The codec has already been optimised a lot. There's some further potential by using both CPU cores on PortalPlayer targets.
Approximate decoding speed for v3.99 files on the various CPUs in Rockbox-supported DAPs are as follows (figures for 44.1kHz 16 bit stereo files):

Devices	SVN rev. (1)	-c1000	-c2000	-c3000	-c4000	-c5000
iPod 1st Gen..3rd Gen (80MHz ARM7TDMI: PP5002)	r24512	166%	111%	69%	16% (2)	2.0% (2)(3)
iPod 4th Gen, Mini 1st Gen; Iriver H10; m:robe 100 (80MHz ARM7TDMI: PP5020)	r24512	153%	101%	63%	23%	2.8% (3)
iPod 5th Gen, Mini 2nd Gen, Nano 1st Gen; Sansa c200, e200 (80MHz ARM7TDMI: PP5022/PP5024)	r24572	169%	112%	70%	24%	? (2)
Iriver H1x0/H300, iAudio X5/M5/M3 (124 MHz ColdFire 5249/5250)	r24512	258%	185%	133%	55%	13.5%
iPod Nano 2nd Gen (192MHz ARM940T: S5L8701?)	r24786	433%	289%	187%	64%	2.6%
Cowon D2 (192MHz ARM926EJ-S: TCC7801)	r24590	461%	330%	221%	86%	20%
Gigabeat F (300MHz ARM920T: S3C2440?)	r24512	654%	458%	294%	106%	22%
Gigabeat S (528MHz ARM1136JF-S: i.MX31L)	r26004	1378%	1034%	824%	404%	112%
Sansa Clip (250MHz ARM9TDMI: AS3525)	r21234	668%	446%	275%	97%	9%
Sansa Clipv2 (250MHz ARM926EJ-S: AS3525v2)	r27897	580%	409%	274%	108%	26%

1. starting with r24512, tests are done using the standard test files.Differences to earlier tests are minimal (<1% relative).
2. filter buffer(s) taken out of IRAM in favour of a larger reciprocal table for optimised division.
3. insane filter buffer does not fit into IRAM.

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CategorySoundCodecs: Monkey's Audio (APE)