On Tue, Sep 22, 2009 at 4:30 PM, Jose Rafael Pacheco
<jose_rafael_pach...@yahoo.es> wrote:
> Hello,
>
> I want to read from a binary file called myaudio.dat
> Then I've tried the next code:
>
> import struct
> name = "myaudio.dat"
> f = open(name,'rb')
> f.seek(0)
Don't bother to seek(0) on a file you just opened.
> chain = "< 4s 4s I 4s I 20s I I i 4s I 67s s 4s I"
> s = f.read(4*1+4*1+4*1+4*1+4*1+20*1+4*1+4*1+4*1+4*1+4*1+67*1+1+4*1+4*1)
Instead of calculating the size of the data represented by the format,
instead use the struct.calcsize() function
s = f.read(struct.calcsize(chain))
> a = struct.unpack(chain, s)
> header = {'identifier' : a[0],
> 'cid' : a[1],
> 'clength' : a[2],
> 'hident' : a[3],
> 'hcid32' : a[4],
> 'hdate' : a[5],
> 'sampling' : a[6],
> 'length_B' : a[7],
> 'max_cA' : a[8],
> 'max_cA1' : a[9],
> 'identNOTE' : a[10],
> 'c2len' : a[11],}
>
> It produces:
>
> {'length_B': 150001, 'sampling': 50000, 'max_cA1': 'NOTE', 'hident': 'HEDR',
> 'c2len': "Normal Sustained Vowel 'A', Voice and Speech Lab., MEEI, Boston,
> MA", 'hdate': 'Jul 13 11:57:41 1994', 'identNOTE': 68, 'max_cA': -44076,
> 'cid': 'DS16', 'hcid32': 32, 'identifier': 'FORM', 'clength': 300126}
>
> So far when I run f.tell()
>>>f.tell()
> 136L
>
> The audio data length is 300126, now I need a clue to build an array with
> the audio data (The Chunk SDA_), would it possible with struct?, any help ?
Read the chunk ID and length and then use the length to read the rest
of the chunk data.
> Thanks
>
> The file format is:
>
>
> Offset | Length | Type | Contents
> 0 4 character Identifier: "FORM"
> 4 4 character Chunk identifier: "DS16"
> 8 4 integer Chunk length
> 12 - - Chunk data
>
> Header 2
>
> Offset Length Type Contents
> 0 4 character Identifier: "HEDR" or "HDR8"
> 4 4 integer Chunk length (32)
> 8 20 character Date, e.g. "May 26 23:57:43 1995"
> 28 4 integer Sampling rate
> 32 4 integer Data length (bytes)
> 36 2 unsigned integer Maximum absolute value for channel A:
> 0xFFFF if not defined
> 38 2 unsigned integer Maximum absolute value for channel A:
> 0xFFFF if not defined
>
> NOTE Chunk
>
> Offset Length Type Contents
> 0 4 character Identifier: "NOTE"
> 4 4 integer Chunk length
> 8 - character Comment string
>
> SDA_, SD_A or SDAB Chunk
> Offset Length Type Contents
> 0 4 character Identifier: "SDA_", "SD_B", or "SDAB"
> 4 4 integer Chunk length
> 8 - - Data
>
>
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>
>
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