func getModeFilter(fh *mp3agic.FrameHeader) uint32 {
if fh.Verify() != nil {
return 0
}
if fh.Channels() == 1 {
return FILTER_MONO
}
return FILTER_STEREO
}
func getLayerFilter(fh *mp3agic.FrameHeader) uint32 {
if fh.Verify() != nil {
return 0
}
switch fh.Layer() {
case mp3agic.MPEG_LAYER_1:
return FILTER_LAYER1
case mp3agic.MPEG_LAYER_2:
return FILTER_LAYER2
case mp3agic.MPEG_LAYER_3:
return FILTER_LAYER3
}
return 0
}
func getSamplingrateFilter(fh *mp3agic.FrameHeader) uint32 {
if fh.Verify() != nil {
return 0
}
switch fh.SampleRate() {
case 32000, 16000, 8000:
return FILTER_32000HZ
case 44100, 22050, 11025:
return FILTER_44100HZ
case 48000, 24000, 12000:
return FILTER_48000HZ
}
return 0
}
func getMpegFilter(fh *mp3agic.FrameHeader) uint32 {
if fh.Verify() != nil {
return 0
}
switch fh.Version() {
case mp3agic.MPEG_VERSION_1_0:
return FILTER_MPEG1
case mp3agic.MPEG_VERSION_2_0:
return FILTER_MPEG2
case mp3agic.MPEG_VERSION_2_5:
return FILTER_MPEG25
}
return 0
}
func constructReservoirFrame(dest []byte, header *mp3agic.FrameHeader, minResSize int, absStartSample int64) int {
// increase for 10-byte-header inclusion
minResSize += 10
h32 := header.getHeader32() | 0x00010000 // switch off CRC usage
fh2 := &FrameHeader{}
for bri := 1; bri <= 14; bri++ {
h32 = (h32 & 0xFFFF0FFF) + (bri << 12)
fh2.setHeader32(h32)
frameSize := fh2.getFrameSize()
sideInfoEnd := fh2.getSideInfoEnd()
mainDataBlockSize := frameSize - sideInfoEnd
if mainDataBlockSize >= minResSize {
dest[0] = byte(h32 >> 24)
dest[1] = byte(h32 >> 16)
dest[2] = byte(h32 >> 8)
dest[3] = byte(h32)
fill(dest[4:sideInfoEnd], 0)
fill(dest[sideInfoEnd:frameSize], 0x78)
// Arrays.fill(dest, 4, sideInfoEnd, (byte) 0);
// Arrays.fill(dest, sideInfoEnd, frameSize, (byte) 0x78);
copy(dest[sideInfoEnd:], []byte("PCUT"))
// dest[sideInfoEnd] = 0x50; // P
// dest[sideInfoEnd + 1] = 0x43; // C
// dest[sideInfoEnd + 2] = 0x55; // U
// dest[sideInfoEnd + 3] = 0x54; // T
copy(dest[sideInfoEnd+4:], []byte{
// revision 0
0,
// absolute sample start pos
byte(uint64(absStartSample) >> 32),
byte(uint64(absStartSample) >> 24),
byte(uint64(absStartSample) >> 16),
byte(uint64(absStartSample) >> 8),
byte(uint64(absStartSample))})
return frameSize
}
}
return -1
}
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
}
