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bytes float and sound

Apr 6, 2011 9:27 AM



I'm trying to do something simple:

send a byteArray to a C library, fill up a buffer and read the memory, but I think I have float conversion problems.


Here is what I do in AS:


var memory:ByteArray = gstate.ds;

// get sound

var soundBytes:ByteArray = new ByteArray();
_source.extract(soundBytes, 4096);

soundBytes.position = 0;

// send sound


// get sound back to play it

memory.position = _dataPosition;


The C code:


My buffer variable:

float *buffer;


The buffer is intialize at the beginning:

static AS3_Val initByteArray(void* self, AS3_Val args) {
    AS3_ArrayValue(args, "IntType", &bufferSize);
    buffer = (float*)malloc(bufferSize*sizeof(float));
    return AS3_Int((int)buffer);


And I process the sound:


AS3_Val src = AS3_Undefined();

AS3_ArrayValue( args,"AS3ValType", &src );

// get length

AS3_Val lengthOfArgs = AS3_GetS(src,"length");
int len = AS3_IntValue(lengthOfArgs);

// set position to 0 and write the buffer

AS3_ByteArray_seek(src, 0, SEEK_SET);
AS3_Trace(AS3_GetS(src, "bytesAvailable"));
AS3_ByteArray_readBytes(buffer, src, len);


Now I get the error:

Exception fault: RangeError: Error #2004: One of the parameters is invalid.


The memory seems to be increased correctly when I write in the buffer, 32768 for 4096 * 8 (4 for float times 2 for left and right channel).

When I trace the bytes in flash before sending the byteArray, I get some numbers like this (at a specific position of 1421 to compare):

soundBytes.position = 1421 * 8;
trace(soundBytes.readFloat()); // trace -0.000030517578125 (left)
trace(soundBytes.readFloat()); // trace 0.000030517578125 (right)


I can trace the same number in C:

AS3_ByteArray_seek(src, 1421*8, SEEK_SET);
AS3_Val emptyParams = AS3_Array("");
AS3_Val readFloat = AS3_GetS(src, "readFloat");
AS3_Val left = AS3_Call(readFloat, src, emptyParams);
AS3_Trace(left); // trace -0.000030517578125 (left)
AS3_Val right = AS3_Call(readFloat, src, emptyParams);
AS3_Trace(right); // trace 0.000030517578125 (right)


But when I trace the buffer:

AS3_Trace(AS3_Number(buffer[1421*2])); // trace 2.5783891743576634e-43
AS3_Trace(AS3_Number(buffer[(1421*2)+1])); trace 7.847271400218976e-44


And in flash after calling the lib:

soundBytes.position = 1421 * 8;
trace(soundBytes.readFloat()); // trace 2.5783891743576634e-43
trace(soundBytes.readFloat()); // trace 7.847271400218976e-44


I looks like the number has been converted or has a different type/format:





I'm not that fluent in C, any idea of what's happening?


Thanks for reading.



  • Currently Being Moderated
    Apr 6, 2011 9:43 AM   in reply to rquantin

    Hi Romu,


    I think it may be the endian issue. Since when you create new ByteArray in ActionScript it is big-endian by default. But the C memory ByteArray is little endian. Try to change it to little endian:

    var soundBytes:ByteArray = new ByteArray();

    soundBytes.endian = Endian.LITTLE_ENDIAN;

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