func (m *scannedMp3) crop(startSample, endSample int64, ips io.Reader, ops io.Writer) os.Error {
//defer ips.Close() // FIXME: leave this to caller
startSample = maxInt64(startSample, int64(-m.encDelay))
endSample = minInt64(endSample, m.SampleCount()+int64(m.encPadding))
maskAth := 0xff
if startSample != 0 {
maskAth &= MASK_ATH_KILL_NO_GAP_START
}
if endSample != m.SampleCount() {
maskAth &= MASK_ATH_KILL_NO_GAP_END
}
firstFrameInclusive := max(0, int((startSample+int64(m.encDelay-minOverlapSamplesStart))/int64(m.samplesPerFrame)))
lastFrameExclusive := min(m.musicFrameCount, int(
(endSample+int64(m.encDelay+minOverlapSamplesEnd+m.samplesPerFrame-1))/int64(m.samplesPerFrame)))
newEncDelay := m.encDelay + int(startSample-int64(firstFrameInclusive)*int64(m.samplesPerFrame))
newEncPadding := int(int64(lastFrameExclusive-firstFrameInclusive)*
int64(m.samplesPerFrame) - int64(newEncDelay) - (endSample - startSample))
accessFrameRecord(firstFrameInclusive)
needBytesFromReservoir := getBitResPtr()
gotBytesFromReservoir := 0
needPreFrames := 0
for firstFrameInclusive-needPreFrames > 0 &&
needBytesFromReservoir > gotBytesFromReservoir &&
newEncDelay+1152 <= 4095 {
needPreFrames++
accessFrameRecord(firstFrameInclusive - needPreFrames)
gotBytesFromReservoir += getMainDataSectionSize()
}
var resFrame []byte
resFrameSize := 0
firstFrameNum := firstFrameInclusive
if needPreFrames == 0 {
// force writing of PCUT tag frame
needPreFrames = 1
}
if needPreFrames > 0 {
firstFrameNum--
newEncDelay += m.samplesPerFrame
resFrame = make([]byte, MAX_MPAFRAME_SIZE)
var newAbsStartSample int64 = startSample
if m.startSample != UNKNOWN_START_SAMPLE {
newAbsStartSample += m.startSample
}
resFrameSize = constructReservoirFrame(resFrame, m.firstFrameHeader,
needBytesFromReservoir, newAbsStartSample)
}
seekTable := make([]byte, 100)
var avgBytesPerFrame, avgBytesPerSecnd, avgkbps float32
musiLen := 0
{ // calculate seek table
accessFrameRecord(firstFrameInclusive)
ofs00 := getFrameFileOfs() - resFrameSize
accessFrameRecord(max(0, lastFrameExclusive-1))
ofsXX := getFrameFileOfs() + getFrameSize()
musiLen = ofsXX - ofs00
avgBytesPerFrame = float32(ofsXX-ofs00) /
float32(lastFrameExclusive-firstFrameInclusive)
avgBytesPerSecnd = avgBytesPerFrame * float32(m.firstFrameHeader.SampleRate()) /
float32(m.firstFrameHeader.SamplesPerFrame())
avgkbps = avgBytesPerSecnd / float32(125)
for i := 0; i < 100; i++ {
fidx := round(float32(firstFrameInclusive+i+1) / 101.0 *
float32(lastFrameExclusive-firstFrameInclusive))
accessFrameRecord(max(0, fidx))
seekTable[i] = byte(round(float32(getFrameFileOfs()-ofs00) * float32(255) /
float32(ofsXX-ofs00)))
}
}
frameBuff := make([]byte, MAX_MPAFRAME_SIZE)
fl := XingInfoLameTagFrame.createHeaderFrame(firstFrameHeader, isVBR, avgkbps,
lastFrameExclusive-firstFrameNum, musiLen, 50, seektable, newEncDelay,
newEncPadding, xiltFrame, frameBuff, 0, maskATH)
ops.write(frameBuff, 0, fl)
filepos := 0
sideInfoSize := firstFrameHeader.getSideInfoSize()
bitRes := 0
if needPreFrames > 0 {
reservoir = make([]byte, 511)
if needBytesFromReservoir > 0 {
for fi := firstFrameInclusive - needPreFrames; fi < firstFrameInclusive; fi++ {
accessFrameRecord(fi)
tmp := getFrameFileOfs()
ips.skip(tmp - filepos)
filepos = tmp
fl = getFrameSize()
readFully(ips, frameBuff, 0, fl)
filepos += fl
mdss := getMainDataSectionSize()
if mdss >= 511 {
copy(reservoir, frameBuff[fl-511:])
// System.arraycopy(frameBuff, fl - 511, reservoir, 0, 511);
} else {
move := 511 - mdss
copy(reservoir[:move], reservoir[511-move:])
copy(reservoir[move:], frameBuff[fl-mdss:])
// System.arraycopy(reservoir, 511 - move, reservoir, 0, move);
// System.arraycopy(frameBuff, fl - mdss, reservoir, move, mdss);
}
}
copy(resFrame[resFrameSize-needBytesFromReservoir:resFrameSize], reservoir[511-needBytesFromReservoir:])
// System.arraycopy(reservoir, 511 - needBytesFromReservoir, resFrame,
// resFrameSize - needBytesFromReservoir, needBytesFromReservoir);
}
ops.write(resFrame, 0, resFrameSize)
bitRes = needBytesFromReservoir
}
for fi := firstFrameInclusive; fi < lastFrameExclusive; fi++ {
accessFrameRecord(fi)
tmp := getFrameFileOfs()
ips.skip(tmp - filepos)
filepos = tmp
fl = getFrameSize()
readFully(ips, frameBuff, 0, fl)
filepos += fl
tmp = getBitResPtr()
if tmp > bitRes {
silenceFrame(frameBuff, 0, sideInfoSize)
}
ops.Write(frameBuff[:fl])
tmp = getMainDataSectionSize()
bitRes = min(bitRes+tmp, maxRes)
}
}