https://wiki.multimedia.cx/api.php?action=feedcontributions&feedformat=atom&user=Ek1Mpj 2026-09-28T17:07:34Z User contributions MediaWiki 1.39.5 https://wiki.multimedia.cx/index.php?title=Xan_DPCM&diff=7652 2007-04-11T06:49:02Z

<p>Ek1Mpj: </p> <hr /> <div>Company: [[Origin Systems]]<br /> <br /> Origin's [http://www.mobygames.com/game/dos/wing-commander-iv-the-price-of-freedom Wing Commander IV: The Price of Freedom] computer game transports multimedia cutscenes in standard Microsoft [[Microsoft Audio/Video Interleaved|AVI]] files. The audio in these files is encoded using a custom format that this page takes the liberty of naming Xan DPCM.<br /> <br /> Note that an AVI file demuxer will probably need to be modified to support the algorithm. The [[WAVEFORMATEX]] headers in the Xan AVI files report the audio coding as format 0x0001: [[PCM]]. However, the file's 'auds' chunk begins with the fourcc 'Axan'. A program can either check for this or assume that the file uses Xan DPCM if it uses [[Origin Xan Codec|Xan]] video.<br /> <br /> Classifying the Xan audio coding method as a DPCM algorithm is a little shaky. It actually resembles a cross between a DPCM algorithm and a APDCM algorithm. Perhaps the designers could not decide between the two algorithm families and decided to split the difference. The algorithm encodes 16-bit PCM samples as 8-bit bytes by packing a 6-bit delta value along with a 2-bit delta modifier into a byte.<br /> <br /> For each chunk of Xan DPCM data, the first 2 or 4 bytes are the initial predictors for that chunk, depending on mono or stereo data, and are encoded as signed, 16-bit, little-endian numbers. A shifter value for each channel is initialized to 4. For each byte in the stream (assuming mono data):<br /> <br /> byte = next byte in stream<br /> diff = (byte</div>

Ek1Mpj