+shared_ptr<ContentAudio>
+AudioDecoder::get_audio (AudioFrame frame, AudioFrame length, bool accurate)
+{
+ shared_ptr<ContentAudio> dec;
+
+ AudioFrame const end = frame + length - 1;
+
+ if (frame < _decoded_audio.frame || end > (_decoded_audio.frame + length * 4)) {
+ /* Either we have no decoded data, or what we do have is a long way from what we want: seek */
+ seek (ContentTime::from_frames (frame, _audio_content->content_audio_frame_rate()), accurate);
+ }
+
+ AudioFrame decoded_offset = 0;
+
+ /* Now enough pass() calls will either:
+ * (a) give us what we want, or
+ * (b) hit the end of the decoder.
+ *
+ * If we are being accurate, we want the right frames,
+ * otherwise any frames will do.
+ */
+ if (accurate) {
+ while (!pass() && _decoded_audio.audio->frames() < length) {}
+ /* Use decoded_offset of 0, as we don't really care what frames we return */
+ } else {
+ while (!pass() && (_decoded_audio.frame > frame || (_decoded_audio.frame + _decoded_audio.audio->frames()) < end)) {}
+ decoded_offset = frame - _decoded_audio.frame;
+ }
+
+ AudioFrame const amount_left = _decoded_audio.audio->frames() - decoded_offset;
+
+ AudioFrame const to_return = min (amount_left, length);
+ shared_ptr<AudioBuffers> out (new AudioBuffers (_decoded_audio.audio->channels(), to_return));
+ out->copy_from (_decoded_audio.audio.get(), to_return, decoded_offset, 0);
+
+ /* Clean up decoded */
+ _decoded_audio.audio->move (decoded_offset + to_return, 0, amount_left - to_return);
+ _decoded_audio.audio->set_frames (amount_left - to_return);
+
+ return shared_ptr<ContentAudio> (new ContentAudio (out, frame));
+}
+
+/** Called by subclasses when audio data is ready.
+ *
+ * Audio timestamping is made hard by many factors, but perhaps the most entertaining is resampling.