Electronic Arts AS4 / ASF Music - Revision history

Sembiance: Added sample files

2023-12-28T21:21:01Z

Added sample files

Jsummers: PRONOM

2016-10-28T14:53:45Z

PRONOM

Dan Tobias at 02:59, 14 May 2014

2014-05-14T02:59:11Z

Halftheisland: Created page with "{{FormatInfo |formattype=electronic |subcat=Audio and Music |extensions={{ext|as4}} {{ext|asf}} }} == Description == AS4 / ASF files are an audio file format used in many vi..."

2013-10-03T12:14:08Z

Created page with "{{FormatInfo |formattype=electronic |subcat=Audio and Music |extensions={{ext|as4}} {{ext|asf}} }} == Description == AS4 / ASF files are an audio file format used in many vi..."

New page

{{FormatInfo
|formattype=electronic
|subcat=Audio and Music
|extensions={{ext|as4}} {{ext|asf}}
}}

== Description ==

AS4 / ASF files are an audio file format used in many video games created by Electronic Arts. Note that extensions other than those listed may be AS4 / ASF files as Electronic Arts often change file extensions for different games.

== Information ==

The basic structure of AS4 / ASF files is similar to that of [[RIFF]], with each file divided into blocks (although, unlike [[RIFF]], the format does not have a global file header).

Each block starts with a standard header:

<pre>
struct ASFBlockHeader
{
char szBlockID[4];
DWORD dwSize;
};
</pre>

Where:

* ''szBlockID'' gives the string ID for the block
* ''dwSize'' gives the size of the block (including the header) in bytes.

Each file then consists of a number of blocks, each of which are described below.

=== Header Block ===

Block ID:'''1SNh'''

This is the first block in an ASF / AS4 file, describing the audio stream.

<pre>
struct EACSHeader
{
char szID[4];
DWORD dwSampleRate;
BYTE bBits;
BYTE bChannels;
BYTE bCompression;
BYTE bType;
DWORD dwNumSamples;
DWORD dwLoopStart;
DWORD dwLoopLength;
DWORD dwDataStart;
DWORD dwUnknown;
};
</pre>

* ''szID'' - the ID string, should always be "EACS"
* ''dwSampleRate'' - the sample rate for the file
* ''bBits'' - the resolution of the decompressed sound data, divided by 8 (i.e. 1 = 8-bit, 2 = 16-bit)
* ''bChannels'' - the number of channels. There are only two options: 1 for mono, 2 for stereo
* ''bCompression'' - if this is equal to 0x00, the audio data consists of signed 8 or 16-bit [[PCM]]. If it is equal to 0x02, the audio data consists of compressed [[IMA ADPCM]]
* ''bType'' - the type of file (this should always be 0x00 for AS4 / ASF files)
* ''dwNumSamples'' - the number of samples in the file
* ''dwLoopStart'' - where the beginning of the repeat loop should start (in terms of samples). If this is 0xFFFFFFFF, there is no loop
* ''dwLoopLength'' - the length of the repeat loop (again in samples). If this is 0, there is no loop
* ''dwDataStart'' - this is not used for AS4 / ASF files
* ''dwUnknown'' - as the name suggests, the function of this would appear to be unknown

=== Sound Data ===

Block ID: '''1SNd'''

The next block following the header is the sound data block. Confusingly, the first chunk of sound data will be contained in the '''1SNh''' block.

<pre>
struct ASFChunkHeader
{
DWORD dwOutSize;
LONG lIndexLeft;
LONG lIndexRight;
LONG lCurSampleLeft;
LONG lCurSampleRight;
};
</pre>

* ''dwOutSize'' - the size of the uncompressed (8 or 16-bit [[PCM]]) data in the chunk (in terms of samples).
* ''lIndexLeft'', ''lIndexRight'', ''lCurSampleLeft'', ''lCurSampleRight'' - these are the initial values for the [[IMA ADPCM]] decompression routine.

As mentioned above, if no compression is used these blocks consist simply of signed 8 or 16-bit [[PCM]] audio. Also note that for mono files, there is no ''lIndexRight'' or
''lCurSampleRight'' value.

=== Loop Block ===

Block ID: '''1SNl'''

This consists of a single value, ''DWORD value'', which defines the looping jump position relative to the start of the song. This block may be followed by a number of further '''1SNd''' blocks.

=== End Block ===

Block ID: '''1SNe'''

An 8-byte block containing no data that defines the end of the audio stream. If there is a loop, the jump should be made from here. Note that some files contain further audio data beyond this.

== Software ==

* http://bim.km.ru/gap/

== Links ==

* http://www.extractor.ru/articles/electronic_arts_audio_file_formats_description

← Older revision		Revision as of 02:59, 14 May 2014
Line 107:		Line 107:

	* http://www.extractor.ru/articles/electronic_arts_audio_file_formats_description		* http://www.extractor.ru/articles/electronic_arts_audio_file_formats_description
		+
		+	[[Category:Electronic Arts]]

@@ Line 7: / Line 7: @@
 == Description ==
 AS4 / ASF files are an audio file format used in many video games created by Electronic Arts. Note that extensions other than those listed may be AS4 / ASF files as Electronic Arts often change file extensions for different games.
 == Information ==
 The basic structure of AS4 / ASF files is similar to that of [[RIFF]], with each file divided into blocks (although, unlike [[RIFF]], the format does not have a global file header).
@@ Line 32: / Line 30: @@
 === Header Block ===
 Block ID:'''1SNh'''
@@ Line 67: / Line 64: @@
 === Sound Data ===
 Block ID: '''1SNd'''
@@ Line 90: / Line 86: @@
 === Loop Block ===
 Block ID: '''1SNl'''
@@ Line 96: / Line 91: @@
 === End Block ===
 Block ID: '''1SNe'''
@@ Line 102: / Line 96: @@
 == Software ==
 * http://bim.km.ru/gap/
 == Links ==
 * http://www.extractor.ru/articles/electronic_arts_audio_file_formats_description
 [[Category:Electronic Arts]]

@@ Line 2: / Line 2: @@
 |formattype=electronic
 |subcat=Audio and Music
-|extensions={{ext|as4}} {{ext|asf}}
+|extensions={{ext|as4}}, {{ext|asf}}
 }}