On Mon, 15.12.08 17:12, Baek Chang (baeksan at ccrma.stanford.edu) wrote: Sorry for the late response, > I were to utilize a ramping function to process a block of audio in a > sink-input, where should this be called? I tried using inserting a ramping > routine on a sink-input within pa_sink_input_peek(), in sink-input.c > > This seems to give me strange results. Any suggestions on where I could > process the audio data of individual sink-inputs before it gets mixed down > into a single sink? pa_sink_input_peek() is the right place. But please note that you should advance you state only in pa_sink_input_drop()! The background for this: the render code first calls _peek() for all streams. They might return memory blocks of different sizes. We mix all blocks into a block that has the smallest size of the ones we got. Then we tell all streams with _drop() how many bytes have actually been used. That means: a. If _peek() is called twice in a row without a _drop() in between no samples have been used -- the stream should hence return the same data both times. b. If _peek() returns 200 bytes but _drop() gets only 100 passed, then you should advance your state only by 100, not by 200! Finally, in some situations we might need to rewind the buffers, so that the data can be read again from the streams. The streams are informed about that via pa_sink_input_process_rewind(). So, you need to patch _peek(), _drop() and _process_rewind(). In the first function you apply your ramping. In the second function you advance your state. In the third function you rewind your state. I plan to add new hooks at these three new places so that modules can modify the sound data in arbitrary ways without any further changes in the main code. Lennart -- Lennart Poettering Red Hat, Inc. lennart [at] poettering [dot] net ICQ# 11060553 http://0pointer.net/lennart/ GnuPG 0x1A015CC4
