QAAC

QAAC是一個基於QuickTime API的AAC/ALAC命令行編碼器，是根據qtaacenc改進的音頻編碼器。1.00版之後不再需要QuickTime組件，但仍然需要安裝Apple Application Support以支持運行。

特點

1. 支持AAC-LC, AAC-HE, ALAC編碼，默認使用m4a容器封裝(蘋果公司採用的一種音頻格式)，也可以混流成ADTS

2. 支持Unicode標籤

3. 支持多聲道

4. 支持高解析度多聲道ALAC

5. 支持CUE檔案輸入

使用參數

Usage: qaac [options] infiles....; "-" as infile means stdin.; In ADTS output mode, "-" as outfile means stdout.; Main options: -d <dirname> Output directory, default is cwd; -a, --abr <bitrate> AAC ABR mode / bitrate; -V, --tvbr <n> AAC True VBR mode / quality [0-127]; -v, --cvbr <bitrate> AAC Constrained VBR mode / bitrate; -c, --cbr <bitrate> AAC CBR mode / bitrate; --he HE AAC mode (Can't use TVBR); -A, --alac ALAC encoding mode; -q, --quality <n> AAC encoding Quality [0-2]; -r, --rate <option> Sample rate option (AAC only); Specify one of the followings: keep: Try to preserve the original rate; auto: Let QuickTime choose the optimal one; <number>: Literal rate in Hz; -s, --silent Don't be verbose; -n, --nice Give lower process priority; --downmix <mono|stereo> Downmix to mono/stereo; --no-optimize Don't optimize MP4 container file after encoding; --adts ADTS(raw AAC)output, instead of m4a(AAC only); --ignorelength Assume WAV input and ignore the data chunk length; -R, --raw Raw PCM input; -S, --stat Save bitrate statistics into file; Options for single input mode only: -o <filename> Output filename; Options for Raw PCM input only: --raw-channels <n> Number of channels, default 2; --raw-rate <n> Sample rate, default 44100; --raw-format <str> Sample format, default S16L; Sample format spec: 1st char: S(igned) | U(nsigned) | F(loat); 2nd part: Bitwidth; Last part: L(ittle Endian) | B(ig Endian); Cases are ignored. u8b is OK.

參數說明

iTunes參數	QAAC參數設定
Good Quality(128k)	-a128 -q1
iTunes Plus(256k)	-v256 -q2
Custom (VBR on)	-v <bitrate> -q2
Custom (VBR off)	-a <bitrate> -q2

理論上使用"-v256 -q2" 編碼（-q2 是編碼時默認參數，可以省略）能得出與iTunes Plus一樣的結果。