func (m *scannedMp3) scan(ips io.ReadSeeker) os.Error {
temp := make([]byte, MAX_MPAFRAME_SIZE)
jh := new(MyCountingJunkHandler)
mpafp := &mpaFrameParser{ips: ips, junkh: jh}
filter := FILTER_LAYER3
var fh *mp3agic.FrameHeader
frameCounter := 0
firstFrameFound := false
isMPEG1 := false
firstkbps := 0
sumMusicFrameSize := 0
//try {
for {
fh, err := mpafp.getNextFrame(filter, temp, fh)
if err != nil && err != os.EOF {
return err
}
frameSize := fh.LengthInBytes()
//int frameSize = fh.getFrameSize();
if !firstFrameFound {
firstFrameFound = true
firstkbps = fh.BitrateInKbps()
m.samplesPerFrame = fh.SamplesPerFrame()
isMPEG1 = (fh.Version() == mp3agic.MPEG_VERSION_1_0)
if isMPEG1 {
m.maxRes = 511
} else {
m.maxRes = 255
}
filter = getFilterFor(fh)
m.firstFrameHeader = fh
if m.xiltFrame.parse(temp, 0) {
if m.xiltFrame.hasXingTag {
m.isVBR = true
}
frameCounter--
if m.xiltFrame.hasLameTag {
m.encDelay = m.xiltFrame.encDelay
m.encPadding = m.xiltFrame.encPadding
}
}
} else {
checkBitRate := true
if frameCounter == 0 {
checkBitRate = false
// first music frame. might be a PCUT-tag
// reservoir-filler frame
sie := fh.SideInfoEnd()
// a pcut frame contains its tag in the first 10
// bytes of the
// main data section
pcutFrame := (sie+10 <= frameSize) && (temp[sie] == 0x50) && // P
(temp[sie+1] == 0x43) && // C
(temp[sie+2] == 0x55) && // U
(temp[sie+3] == 0x54) // T
if pcutFrame {
// temp[sie+4] tag revision (always 0 for now)
t := int64(temp[sie+5]) // fetch 40 bit start sample
t = (t << 8) | int64(temp[sie+6])
t = (t << 8) | int64(temp[sie+7])
t = (t << 8) | int64(temp[sie+8])
t = (t << 8) | int64(temp[sie+9])
m.startSample = t
} else {
for b := range temp[fh.SideInfoStart():fh.SideInfoEnd()] {
if b != 0 {
checkBitRate = true
break
}
}
}
}
// we don't want the first "music frame" to be checked
// if it's
// possibly a PCUT generated reservoir frame
if checkBitRate && fh.BitrateInKbps() != firstkbps {
m.isVBR = true
}
}
if frameCounter >= 0 {
sumMusicFrameSize += frameSize
accessFrameRecord(frameCounter)
setFrameFileOfs(int(*jh))
setFrameSize(frameSize)
sis := fh.SideInfoStart()
ofs := sis
brPointer := int(temp[ofs])
if isMPEG1 {
brPointer = (brPointer << 1) | int((temp[ofs+1]&0x80)>>7)
}
setBitResPtr(brPointer)
setMainDataSectionSize(frameSize - sis - fh.SideInfoSize())
}
jh.Inc(frameSize)
frameCounter++
}
//}
//catch (EOFException x) {
//}
m.musicFrameCount = frameCounter
if !firstFrameFound {
return os.NewError("no mp3 data found")
}
var framerate float32 = float32(m.firstFrameHeader.SampleRate()) /
float32(m.firstFrameHeader.SamplesPerFrame())
m.avgBitrate = (float32(sumMusicFrameSize) / float32(m.musicFrameCount)) * framerate / 125
/*
} finally {
try {
ips.close();
}
catch (IOException x) {
}
}
*/
return nil
}
