The visualizer framerate is lower with FLAC than with MP3. This is primarily a result of the firmware audio pipeline and FLAC decoder architecture, and secondarily because of the size of FLAC frames. From what I can tell, FLAC decompression itself doesn't put a greater load on the SB2 CPU than MP3.
The decoding process and visualizer computation run on the same thread in firmware. Visualizer frames are computed between invocations of the decoder. Any single invocation of the FLAC decoder results in decompression of a complete FLAC frame. The state machine within the FLAC decoder doesn't allow for decompression of a partial FLAC frame - as a result the thread effectively blocks till an entire frame has been decoded. Because of the size of a FLAC frame (~1/10th of a second of audio) this can take more time than the goal frame period of the visualizer (30 fps = ~33ms). The SB2 CPU architecture allows for 8 concurrent threads, so several other processes, including screen updates, network activity and audio processing (e.g. application of gain) can occur during this period...just not visualizer computation. The MP3 decoder in the SB2 has a finer grained state machine and smaller frame sizes - this results in a higher framerate. Neither decoder comes even close to pegging the CPU. -- vidurapparao _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
