Re: Data Types for Extracting samples from Audio Buffer

Mon, 06 Oct 2008 06:13:06 -0700 

That doesn't seem to be it.

The audio extraction interface
http://developer.apple.com/quicktime/audioextraction.html
returns:
2008-10-06 09:08:03.106 Roboplasm[33253:813]    format flags            = 41
2008-10-06 09:08:03.106 Roboplasm[33253:813] sample rate = 48000.000000 
2008-10-06 09:08:03.107 Roboplasm[33253:813]    bytes/packet     = 4
2008-10-06 09:08:03.108 Roboplasm[33253:813]    frames/packe     = 1
2008-10-06 09:08:03.108 Roboplasm[33253:813]    bytes/frame      = 4
2008-10-06 09:08:03.109 Roboplasm[33253:813]    channels/frame  = 2
2008-10-06 09:08:03.109 Roboplasm[33253:813]    bits/channel     = 32
2008-10-06 09:08:03.109 Roboplasm[33253:813]    format flags            = 41
2008-10-06 09:08:03.110 Roboplasm[33253:813] sample rate = 48000.000000 
2008-10-06 09:08:03.110 Roboplasm[33253:813]    bytes/packet     = 4
2008-10-06 09:08:03.110 Roboplasm[33253:813]    frames/packet    = 1
2008-10-06 09:08:03.110 Roboplasm[33253:813]    bytes/frame      = 4
2008-10-06 09:08:03.111 Roboplasm[33253:813]    channels/frame  = 2
2008-10-06 09:08:03.111 Roboplasm[33253:813]    bits/channel     = 32
Indicating that there are two bytes per channel.

Results from
        unsigned long *ippointer =  (unsigned long *)abl->mBuffers[0].mData;
        unsigned long *idpointer =  (unsigned long *)abl->mBuffers[1].mData;
        ipbuf = [[NSMutableArray alloc] init];
        idbuf = [[NSMutableArray alloc] init];
        NSNumber* ipsamp = [[NSNumber alloc] init];
        NSNumber* idsamp = [[NSNumber alloc] init];
        nsamples = (abl->mBuffers[0].mDataByteSize)/4;

for (isamp = 0; isamp<nsamples; ++isamp){
ipsamp = [NSNumber numberWithUnsignedLong:(unsigned long)ippointer[isamp]]; 
                     [ipbufaddObject:ipsamp];
idsamp = [NSNumber numberWithUnsignedLong:(unsigned long)idpointer[isamp]]; 
                     [idbufaddObject:idsamp];
        if (isamp < 100) {
                NSLog(@" isamp %d ipsamp %@ idsamp %@",isamp,ipsamp,idsamp);
        }       
}

Are:
2008-10-06 09:08:03.150 Roboplasm[33253:813] isamp 0 ipsamp 995885056 idsamp 997064704 2008-10-06 09:08:03.152 Roboplasm[33253:813] isamp 1 ipsamp 997326848 idsamp 998834176 2008-10-06 09:08:03.152 Roboplasm[33253:813] isamp 2 ipsamp 999424000 idsamp 1000931328 2008-10-06 09:08:03.152 Roboplasm[33253:813] isamp 3 ipsamp 999292928 idsamp 1004470272 2008-10-06 09:08:03.153 Roboplasm[33253:813] isamp 4 ipsamp 995622912 idsamp 1006370816 2008-10-06 09:08:03.153 Roboplasm[33253:813] isamp 5 ipsamp 991428608 idsamp 1005584384 2008-10-06 09:08:03.153 Roboplasm[33253:813] isamp 6 ipsamp 991035392 idsamp 1005387776 2008-10-06 09:08:03.154 Roboplasm[33253:813] isamp 7 ipsamp 992215040 idsamp 1007288320 2008-10-06 09:08:03.154 Roboplasm[33253:813] isamp 8 ipsamp 993787904 idsamp 1008435200 2008-10-06 09:08:03.154 Roboplasm[33253:813] isamp 9 ipsamp 997064704 idsamp 1007616000 2008-10-06 09:08:03.154 Roboplasm[33253:813] isamp 10 ipsamp 999030784 idsamp 1004929024 2008-10-06 09:08:03.155 Roboplasm[33253:813] isamp 11 ipsamp 998572032 idsamp 1003749376 2008-10-06 09:08:03.155 Roboplasm[33253:813] isamp 12 ipsamp 994836480 idsamp 1005715456 2008-10-06 09:08:03.158 Roboplasm[33253:813] isamp 13 ipsamp 991428608 idsamp 1007321088 2008-10-06 09:08:03.158 Roboplasm[33253:813] isamp 14 ipsamp 991559680 idsamp 1008074752 2008-10-06 09:08:03.158 Roboplasm[33253:813] isamp 15 ipsamp 995622912 idsamp 1008599040 2008-10-06 09:08:03.159 Roboplasm[33253:813] isamp 16 ipsamp 999948288 idsamp 1008566272 2008-10-06 09:08:03.159 Roboplasm[33253:813] isamp 17 ipsamp 1002176512 idsamp 1008041984 2008-10-06 09:08:03.159 Roboplasm[33253:813] isamp 18 ipsamp 1002962944 idsamp 1007943680 2008-10-06 09:08:03.160 Roboplasm[33253:813] isamp 19 ipsamp 1002700800 idsamp 1008173056 2008-10-06 09:08:03.160 Roboplasm[33253:813] isamp 20 ipsamp 1002242048 idsamp 1007616000 2008-10-06 09:08:03.160 Roboplasm[33253:813] isamp 21 ipsamp 1002766336 idsamp 1006731264 2008-10-06 09:08:03.160 Roboplasm[33253:813] isamp 22 ipsamp 1005256704 idsamp 1006764032 2008-10-06 09:08:03.161 Roboplasm[33253:813] isamp 23 ipsamp 1007517696 idsamp 1007157248 2008-10-06 09:08:03.161 Roboplasm[33253:813] isamp 24 ipsamp 1008140288 idsamp 1007058944 2008-10-06 09:08:03.162 Roboplasm[33253:813] isamp 25 ipsamp 1007779840 idsamp 1007321088 2008-10-06 09:08:03.162 Roboplasm[33253:813] isamp 26 ipsamp 1007779840 idsamp 1008500736 2008-10-06 09:08:03.163 Roboplasm[33253:813] isamp 27 ipsamp 1008795648 idsamp 1008893952 2008-10-06 09:08:03.163 Roboplasm[33253:813] isamp 28 ipsamp 1009385472 idsamp 1007779840 2008-10-06 09:08:03.163 Roboplasm[33253:813] isamp 29 ipsamp 1008402432 idsamp 1006665728 2008-10-06 09:08:03.163 Roboplasm[33253:813] isamp 30 ipsamp 1006993408 idsamp 1006567424 2008-10-06 09:08:03.164 Roboplasm[33253:813] isamp 31 ipsamp 1006862336 idsamp 1006796800 2008-10-06 09:08:03.164 Roboplasm[33253:813] isamp 32 ipsamp 1007583232 idsamp 1006796800 2008-10-06 09:08:03.164 Roboplasm[33253:813] isamp 33 ipsamp 1008041984 idsamp 1007255552 2008-10-06 09:08:03.165 Roboplasm[33253:813] isamp 34 ipsamp 1008107520 idsamp 1008336896 2008-10-06 09:08:03.170 Roboplasm[33253:813] isamp 35 ipsamp 1007583232 idsamp 1009451008 2008-10-06 09:08:03.173 Roboplasm[33253:813] isamp 36 ipsamp 1006632960 idsamp 1010106368 2008-10-06 09:08:03.174 Roboplasm[33253:813] isamp 37 ipsamp 1006632960 idsamp 1009909760 2008-10-06 09:08:03.174 Roboplasm[33253:813] isamp 38 ipsamp 1008205824 idsamp 1008893952 2008-10-06 09:08:03.174 Roboplasm[33253:813] isamp 39 ipsamp 1009647616 idsamp 1007812608 2008-10-06 09:08:03.175 Roboplasm[33253:813] isamp 40 ipsamp 1009582080 idsamp 1007321088 2008-10-06 09:08:03.175 Roboplasm[33253:813] isamp 41 ipsamp 1009582080 idsamp 1006960640 2008-10-06 09:08:03.175 Roboplasm[33253:813] isamp 42 ipsamp 1010892800 idsamp 1005912064 2008-10-06 09:08:03.175 Roboplasm[33253:813] isamp 43 ipsamp 1011908608 idsamp 1005256704 2008-10-06 09:08:03.176 Roboplasm[33253:813] isamp 44 ipsamp 1011286016 idsamp 1006501888 2008-10-06 09:08:03.176 Roboplasm[33253:813] isamp 45 ipsamp 1010270208 idsamp 1007190016 2008-10-06 09:08:03.176 Roboplasm[33253:813] isamp 46 ipsamp 1010139136 idsamp 1006698496 2008-10-06 09:08:03.183 Roboplasm[33253:813] isamp 47 ipsamp 1009975296 idsamp 1005125632 2008-10-06 09:08:03.184 Roboplasm[33253:813] isamp 48 ipsamp 1008992256 idsamp 1005846528 2008-10-06 09:08:03.185 Roboplasm[33253:813] isamp 49 ipsamp 1008271360 idsamp 1007484928 2008-10-06 09:08:03.185 Roboplasm[33253:813] isamp 50 ipsamp 1008435200 idsamp 1007648768 2008-10-06 09:08:03.185 Roboplasm[33253:813] isamp 51 ipsamp 1008664576 idsamp 1005060096 2008-10-06 09:08:03.186 Roboplasm[33253:813] isamp 52 ipsamp 1008992256 idsamp 1000275968 2008-10-06 09:08:03.187 Roboplasm[33253:813] isamp 53 ipsamp 1010499584 idsamp 997064704 2008-10-06 09:08:03.188 Roboplasm[33253:813] isamp 54 ipsamp 1012465664 idsamp 995753984 2008-10-06 09:08:03.188 Roboplasm[33253:813] isamp 55 ipsamp 1013252096 idsamp 993656832 2008-10-06 09:08:03.188 Roboplasm[33253:813] isamp 56 ipsamp 1013153792 idsamp 990380032 2008-10-06 09:08:03.189 Roboplasm[33253:813] isamp 57 ipsamp 1013350400 idsamp 988020736 2008-10-06 09:08:03.189 Roboplasm[33253:813] isamp 58 ipsamp 1013514240 idsamp 985137152 2008-10-06 09:08:03.193 Roboplasm[33253:813] isamp 59 ipsamp 1013252096 idsamp 972029952 2008-10-06 09:08:03.194 Roboplasm[33253:813] isamp 60 ipsamp 1013219328 idsamp 3103784960 2008-10-06 09:08:03.194 Roboplasm[33253:813] isamp 61 ipsamp 1013317632 idsamp 973602816 2008-10-06 09:08:03.195 Roboplasm[33253:813] isamp 62 ipsamp 1012891648 idsamp 982777856 2008-10-06 09:08:03.196 Roboplasm[33253:813] isamp 63 ipsamp 1012563968 idsamp 974127104 2008-10-06 09:08:03.196 Roboplasm[33253:813] isamp 64 ipsamp 1013284864 idsamp 3117416448 2008-10-06 09:08:03.197 Roboplasm[33253:813] isamp 65 ipsamp 1014038528 idsamp 3126329344 2008-10-06 09:08:03.198 Roboplasm[33253:813] isamp 66 ipsamp 1013317632 idsamp 3130261504 2008-10-06 09:08:03.199 Roboplasm[33253:813] isamp 67 ipsamp 1011580928 idsamp 3134455808 2008-10-06 09:08:03.199 Roboplasm[33253:813] isamp 68 ipsamp 1010040832 idsamp 3138650112 2008-10-06 09:08:03.199 Roboplasm[33253:813] isamp 69 ipsamp 1009385472 idsamp 3141926912 2008-10-06 09:08:03.200 Roboplasm[33253:813] isamp 70 ipsamp 1009811456 idsamp 3146121216 2008-10-06 09:08:03.200 Roboplasm[33253:813] isamp 71 ipsamp 1011449856 idsamp 3149660160 2008-10-06 09:08:03.200 Roboplasm[33253:813] isamp 72 ipsamp 1013612544 idsamp 3154116608 2008-10-06 09:08:03.201 Roboplasm[33253:813] isamp 73 ipsamp 1015037952 idsamp 3155591168 2008-10-06 09:08:03.201 Roboplasm[33253:813] isamp 74 ipsamp 1015087104 idsamp 3155492864 2008-10-06 09:08:03.201 Roboplasm[33253:813] isamp 75 ipsamp 1014464512 idsamp 3154542592 2008-10-06 09:08:03.202 Roboplasm[33253:813] isamp 76 ipsamp 1013743616 idsamp 3153592320 2008-10-06 09:08:03.202 Roboplasm[33253:813] isamp 77 ipsamp 1013186560 idsamp 3153133568 2008-10-06 09:08:03.202 Roboplasm[33253:813] isamp 78 ipsamp 1012727808 idsamp 3153920000 2008-10-06 09:08:03.203 Roboplasm[33253:813] isamp 79 ipsamp 1012367360 idsamp 3155263488 2008-10-06 09:08:03.203 Roboplasm[33253:813] isamp 80 ipsamp 1011941376 idsamp 3156541440 2008-10-06 09:08:03.203 Roboplasm[33253:813] isamp 81 ipsamp 1011286016 idsamp 3157000192 2008-10-06 09:08:03.204 Roboplasm[33253:813] isamp 82 ipsamp 1010794496 idsamp 3157098496 2008-10-06 09:08:03.204 Roboplasm[33253:813] isamp 83 ipsamp 1011220480 idsamp 3157753856 2008-10-06 09:08:03.204 Roboplasm[33253:813] isamp 84 ipsamp 1012563968 idsamp 3158769664 2008-10-06 09:08:03.205 Roboplasm[33253:813] isamp 85 ipsamp 1013481472 idsamp 3159523328 2008-10-06 09:08:03.206 Roboplasm[33253:813] isamp 86 ipsamp 1013153792 idsamp 3160309760 2008-10-06 09:08:03.207 Roboplasm[33253:813] isamp 87 ipsamp 1012596736 idsamp 3161063424 2008-10-06 09:08:03.208 Roboplasm[33253:813] isamp 88 ipsamp 1012465664 idsamp 3160440832 2008-10-06 09:08:03.208 Roboplasm[33253:813] isamp 89 ipsamp 1012137984 idsamp 3158409216 2008-10-06 09:08:03.209 Roboplasm[33253:813] isamp 90 ipsamp 1011744768 idsamp 3157360640 2008-10-06 09:08:03.210 Roboplasm[33253:813] isamp 91 ipsamp 1011777536 idsamp 3158867968 2008-10-06 09:08:03.211 Roboplasm[33253:813] isamp 92 ipsamp 1011515392 idsamp 3160965120 2008-10-06 09:08:03.212 Roboplasm[33253:813] isamp 93 ipsamp 1010237440 idsamp 3161456640 2008-10-06 09:08:03.212 Roboplasm[33253:813] isamp 94 ipsamp 1009025024 idsamp 3161260032 2008-10-06 09:08:03.213 Roboplasm[33253:813] isamp 95 ipsamp 1008861184 idsamp 3162013696 2008-10-06 09:08:03.213 Roboplasm[33253:813] isamp 96 ipsamp 1008926720 idsamp 3162783744 2008-10-06 09:08:03.213 Roboplasm[33253:813] isamp 97 ipsamp 1008697344 idsamp 3162882048 2008-10-06 09:08:03.214 Roboplasm[33253:813] isamp 98 ipsamp 1008238592 idsamp 3162865664 2008-10-06 09:08:03.214 Roboplasm[33253:813] isamp 99 ipsamp 1007157248 idsamp 3163078656 

Many thanks:

Joseph


On Oct 6, 2008, at 9:01 AM, Graham Cox wrote:



On 6 Oct 2008, at 11:45 pm, Joseph Ayers wrote:
Note the occurrence of samples with the value of 0 alternating with samples that are reasonable. However, this alternation is not rigid as the 0's can be substituted with reasonable numbers. 

Any idea what's going on here?
Are you *sure* that the samples are 16 bit values? Maybe they're 32- bit values, and what you're seeing is the 2 high bytes of each sample being set to zero, but not always. 

Where has the data come from?
If they are 32-bit, make your pointers unsigned long* and divide the bytecount by 4. Also use [NSNumber numberWithUnsignedLong:]; 


hth,

Graham


Joseph Ayers, Professor
Department of Biology and
Marine Science Center
Northeastern University
East Point, Nahant, MA 01908
Phone (781) 581-7370 x309(office), x335(lab)
Boston: 444 Richards Hall (617) 373-4044
Cellular (617) 755-7523, FAX: (781) 581-6076
eMail: [EMAIL PROTECTED]
http://www.neurotechnology.neu.edu/






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