ACT: Difference between revisions

Revision as of 03:39, 30 October 2007

Samples: http://samples.mplayerhq.hu/A-codecs/act/
Working decoder: http://www.netac.com/Download/C635/C635%20Driver&Tools.zip

ACT files are created by Chinese-made portable MP3 players when recording from the internal microphone.

ACT files uses the G729A speech compression codec. There are 3 different ways to record to this format from a player.

Fine Rec
Long Rec
Long Vox, in this mode the player will record when voice activated.

These 3 formats map to 2 bitstream formats, the Fine and Long bitstream formats.

Name	Sample rate	Frame size	Frames per chunk	Chunk size	Padding bytes
Fine	8000	10	51	510	2
Long	4400	22	23	506	6

ACT File Format

Files are always aligned to 512 bytes boundary and contains 512 byte header and chunks of the same size. Each chunk consists of fixed number of frames and padding bytes.

@@ Line 2: / Line 2: @@
 * Working decoder: http://www.netac.com/Download/C635/C635%20Driver&Tools.zip
-ACT is used as codec in is used by [http://en.wikipedia.org/wiki/Chinese_MP4/MTV_Player '''Chinese-made portable MP3 players'''] when recording from the internal microphone.
+ACT files are created by [http://en.wikipedia.org/wiki/Chinese_MP4/MTV_Player '''Chinese-made portable MP3 players'''] when recording from the internal microphone.
-ACT is a low complexity speech compression codec. There are 3 different ways to record to this codec from a player.
+ACT files uses the G729A speech compression codec. There are 3 different ways to record to this format from a player.
-* Fine Rec
+*Fine Rec
-* Long Rec
+*Long Rec
-* Long Vox, in this mode the player will just record if there is anything to record.
+*Long Vox, in this mode the player will record when voice activated.
+These 3 formats map to 2 bitstream formats, the Fine and Long bitstream formats.
+{| border="1" cellpadding="5" style="border-collapse: collapse; border-style: dashed; border-color: #2f6fab;"
+|- bgcolor="#f0f0f0" |
+! Name!! Sample rate!! Frame size!! Frames per chunk !! Chunk size !! Padding bytes
+|-
+|Fine||8000||10||51||510||2
+|-
+|Long||4400||22||23||506||6
+|}
-It is unknown if there are several bitstream formats. With the software that are supposed to convert the files to wav audio are 2 or 3 command line programs. When running one the work G729 is mentioned and the bitrate 4,4k. So an initial guess is that the 3 recording formats are 8kbits, 4.4kbits and 4.4kbits with voice activation. And that the codec actually is G729
 ==ACT File Format==
+Files are always aligned to 512 bytes boundary and contains 512 byte header and chunks of the same size. Each chunk consists of fixed number of frames and padding bytes.
-The first 512 bytes seem to be a regular RIFF header. The function at 0x00401000 is in the call tree when converting act files.
 [[Category:Audio Codecs]]
 [[Category:Undiscovered Audio Codecs]]

ACT: Difference between revisions

Revision as of 03:39, 30 October 2007

ACT File Format

Navigation menu

Search