--- libgig/trunk/src/gig.cpp 2003/12/25 01:09:08 21 +++ libgig/trunk/src/gig.cpp 2003/12/26 16:15:31 24 @@ -315,6 +315,181 @@ } /** + * Reads \a SampleCount number of sample points from the position stored + * in \a pPlaybackState into the buffer pointed by \a pBuffer and moves + * the position within the sample respectively, this method honors the + * looping informations of the sample (if any). The sample wave stream + * will be decompressed on the fly if using a compressed sample. Use this + * method if you don't want to load the sample into RAM, thus for disk + * streaming. All this methods needs to know to proceed with streaming + * for the next time you call this method is stored in \a pPlaybackState. + * You have to allocate and initialize the playback_state_t structure by + * yourself before you use it to stream a sample: + * + * + * gig::playback_state_t playbackstate;
+ * playbackstate.position = 0;
+ * playbackstate.reverse = false;
+ * playbackstate.loop_cycles_left = pSample->LoopPlayCount;
+ * + * + * You don't have to take care of things like if there is actually a loop + * defined or if the current read position is located within a loop area. + * The method already handles such cases by itself. + * + * @param pBuffer destination buffer + * @param SampleCount number of sample points to read + * @param pPlaybackState will be used to store and reload the playback + * state for the next ReadAndLoop() call + * @returns number of successfully read sample points + */ + unsigned long Sample::ReadAndLoop(void* pBuffer, unsigned long SampleCount, playback_state_t* pPlaybackState) { + unsigned long samplestoread = SampleCount, totalreadsamples = 0, readsamples, samplestoloopend; + uint8_t* pDst = (uint8_t*) pBuffer; + + SetPos(pPlaybackState->position); // recover position from the last time + + if (this->Loops && GetPos() <= this->LoopEnd) { // honor looping if there are loop points defined + + switch (this->LoopType) { + + case loop_type_bidirectional: { //TODO: not tested yet! + do { + // if not endless loop check if max. number of loop cycles have been passed + if (this->LoopPlayCount && !pPlaybackState->loop_cycles_left) break; + + if (!pPlaybackState->reverse) { // forward playback + do { + samplestoloopend = this->LoopEnd - GetPos(); + readsamples = Read(&pDst[totalreadsamples * this->FrameSize], Min(samplestoread, samplestoloopend)); + samplestoread -= readsamples; + totalreadsamples += readsamples; + if (readsamples == samplestoloopend) { + pPlaybackState->reverse = true; + break; + } + } while (samplestoread && readsamples); + } + else { // backward playback + + // as we can only read forward from disk, we have to + // determine the end position within the loop first, + // read forward from that 'end' and finally after + // reading, swap all sample frames so it reflects + // backward playback + + unsigned long swapareastart = totalreadsamples; + unsigned long loopoffset = GetPos() - this->LoopStart; + unsigned long samplestoreadinloop = Min(samplestoread, loopoffset); + unsigned long reverseplaybackend = GetPos() - samplestoreadinloop; + + SetPos(reverseplaybackend); + + // read samples for backward playback + do { + readsamples = Read(&pDst[totalreadsamples * this->FrameSize], samplestoreadinloop); + samplestoreadinloop -= readsamples; + samplestoread -= readsamples; + totalreadsamples += readsamples; + } while (samplestoreadinloop && readsamples); + + SetPos(reverseplaybackend); // pretend we really read backwards + + if (reverseplaybackend == this->LoopStart) { + pPlaybackState->loop_cycles_left--; + pPlaybackState->reverse = false; + } + + // reverse the sample frames for backward playback + SwapMemoryArea(&pDst[swapareastart * this->FrameSize], (totalreadsamples - swapareastart) * this->FrameSize, this->FrameSize); + } + } while (samplestoread && readsamples); + break; + } + + case loop_type_backward: { // TODO: not tested yet! + // forward playback (not entered the loop yet) + if (!pPlaybackState->reverse) do { + samplestoloopend = this->LoopEnd - GetPos(); + readsamples = Read(&pDst[totalreadsamples * this->FrameSize], Min(samplestoread, samplestoloopend)); + samplestoread -= readsamples; + totalreadsamples += readsamples; + if (readsamples == samplestoloopend) { + pPlaybackState->reverse = true; + break; + } + } while (samplestoread && readsamples); + + if (!samplestoread) break; + + // as we can only read forward from disk, we have to + // determine the end position within the loop first, + // read forward from that 'end' and finally after + // reading, swap all sample frames so it reflects + // backward playback + + unsigned long swapareastart = totalreadsamples; + unsigned long loopoffset = GetPos() - this->LoopStart; + unsigned long samplestoreadinloop = (this->LoopPlayCount) ? Min(samplestoread, pPlaybackState->loop_cycles_left * LoopSize - loopoffset) + : samplestoread; + unsigned long reverseplaybackend = this->LoopStart + Abs((loopoffset - samplestoreadinloop) % this->LoopSize); + + SetPos(reverseplaybackend); + + // read samples for backward playback + do { + // if not endless loop check if max. number of loop cycles have been passed + if (this->LoopPlayCount && !pPlaybackState->loop_cycles_left) break; + samplestoloopend = this->LoopEnd - GetPos(); + readsamples = Read(&pDst[totalreadsamples * this->FrameSize], Min(samplestoreadinloop, samplestoloopend)); + samplestoreadinloop -= readsamples; + samplestoread -= readsamples; + totalreadsamples += readsamples; + if (readsamples == samplestoloopend) { + pPlaybackState->loop_cycles_left--; + SetPos(this->LoopStart); + } + } while (samplestoreadinloop && readsamples); + + SetPos(reverseplaybackend); // pretend we really read backwards + + // reverse the sample frames for backward playback + SwapMemoryArea(&pDst[swapareastart * this->FrameSize], (totalreadsamples - swapareastart) * this->FrameSize, this->FrameSize); + break; + } + + default: case loop_type_normal: { + do { + // if not endless loop check if max. number of loop cycles have been passed + if (this->LoopPlayCount && !pPlaybackState->loop_cycles_left) break; + samplestoloopend = this->LoopEnd - GetPos(); + readsamples = Read(&pDst[totalreadsamples * this->FrameSize], Min(samplestoread, samplestoloopend)); + samplestoread -= readsamples; + totalreadsamples += readsamples; + if (readsamples == samplestoloopend) { + pPlaybackState->loop_cycles_left--; + SetPos(this->LoopStart); + } + } while (samplestoread && readsamples); + break; + } + } + } + + // read on without looping + if (samplestoread) do { + readsamples = Read(&pDst[totalreadsamples * this->FrameSize], samplestoread); + samplestoread -= readsamples; + totalreadsamples += readsamples; + } while (readsamples && samplestoread); + + // store current position + pPlaybackState->position = GetPos(); + + return totalreadsamples; + } + + /** * Reads \a SampleCount number of sample points from the current * position into the buffer pointed by \a pBuffer and increments the * position within the sample. The sample wave stream will be