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virtual: document how to implement fixed block size filters

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This commit is contained in:
Lennart Poettering 2010-02-25 02:26:03 +01:00
parent 87cc741d0e
commit 34bb996e69
2 changed files with 27 additions and 10 deletions
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33
src/modules/module-virtual-sink.c
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@ -199,7 +199,7 @@ static int sink_input_pop_cb(pa_sink_input *i, size_t nbytes, pa_memchunk *chunk
size_t fs;
unsigned n, c;
pa_memchunk tchunk;
pa_usec_t curr_latency;
pa_usec_t current_latency;
pa_sink_input_assert_ref(i);
pa_assert(chunk);
@ -208,6 +208,10 @@ static int sink_input_pop_cb(pa_sink_input *i, size_t nbytes, pa_memchunk *chunk
/* Hmm, process any rewind request that might be queued up */
pa_sink_process_rewind(u->sink, 0);
/* (1) IF YOU NEED A FIXED BLOCK SIZE USE
* pa_memblockq_peek_fixed_size() HERE INSTEAD. NOTE THAT FILTERS
* WHICH CAN DEAL WITH DYNAMIC BLOCK SIZES ARE HIGHLY
* PREFERRED. */
while (pa_memblockq_peek(u->memblockq, &tchunk) < 0) {
pa_memchunk nchunk;
@ -216,6 +220,8 @@ static int sink_input_pop_cb(pa_sink_input *i, size_t nbytes, pa_memchunk *chunk
pa_memblock_unref(nchunk.memblock);
}
/* (2) IF YOU NEED A FIXED BLOCK SIZE, THIS NEXT LINE IS NOT
* NECESSARY */
tchunk.length = PA_MIN(nbytes, tchunk.length);
pa_assert(tchunk.length > 0);
@ -233,7 +239,7 @@ static int sink_input_pop_cb(pa_sink_input *i, size_t nbytes, pa_memchunk *chunk
src = (float*) ((uint8_t*) pa_memblock_acquire(tchunk.memblock) + tchunk.index);
dst = (float*) pa_memblock_acquire(chunk->memblock);
/* PUT YOUR CODE HERE TO DO SOMETHING WITH THE DATA */
/* (3) PUT YOUR CODE HERE TO DO SOMETHING WITH THE DATA */
/* As an example, copy input to output */
for (c = 0; c < u->channels; c++) {
@ -248,15 +254,14 @@ static int sink_input_pop_cb(pa_sink_input *i, size_t nbytes, pa_memchunk *chunk
pa_memblock_unref(tchunk.memblock);
curr_latency =
/* (4) IF YOU NEED THE LATENCY FOR SOMETHING ACQUIRE IT LIKE THIS: */
current_latency =
/* Get the latency of the master sink */
pa_sink_get_latency_within_thread(i->sink) +
/* Add the latency internal to our sink input on top */
pa_bytes_to_usec(pa_memblockq_get_length(i->thread_info.render_memblockq), &i->sink->sample_spec);
/* FIXME: do something with the latency */
return 0;
}
@ -278,7 +283,7 @@ static void sink_input_process_rewind_cb(pa_sink_input *i, size_t nbytes) {
if (amount > 0) {
pa_memblockq_seek(u->memblockq, - (int64_t) amount, PA_SEEK_RELATIVE, TRUE);
/* PUT YOUR CODE HERE TO RESET POST-PROCESSING */
/* (5) PUT YOUR CODE HERE TO RESET YOUR FILTER */
}
}
@ -304,6 +309,9 @@ static void sink_input_update_max_request_cb(pa_sink_input *i, size_t nbytes) {
pa_sink_input_assert_ref(i);
pa_assert_se(u = i->userdata);
/* (6) IF YOU NEED A FIXED BLOCK SIZE ROUND nbytes UP TO MULTIPLES
* OF IT HERE. THE PA_ROUND_UP MACRO IS USEFUL FOR THAT. */
pa_sink_set_max_request_within_thread(u->sink, nbytes);
}
@ -324,6 +332,10 @@ static void sink_input_update_sink_fixed_latency_cb(pa_sink_input *i) {
pa_sink_input_assert_ref(i);
pa_assert_se(u = i->userdata);
/* (7) IF YOU NEED A FIXED BLOCK SIZE ADD THE LATENCY FOR ONE
* BLOCK MINUS ONE SAMPLE HERE. pa_usec_to_bytes_round_up() IS
* USEFUL FOR THAT. */
pa_sink_set_fixed_latency_within_thread(u->sink, i->sink->thread_info.fixed_latency);
}
@ -348,7 +360,14 @@ static void sink_input_attach_cb(pa_sink_input *i) {
pa_sink_set_rtpoll(u->sink, i->sink->thread_info.rtpoll);
pa_sink_set_latency_range_within_thread(u->sink, i->sink->thread_info.min_latency, i->sink->thread_info.max_latency);
/* (8.1) IF YOU NEED A FIXED BLOCK SIZE ADD THE LATENCY FOR ONE
* BLOCK MINUS ONE SAMPLE HERE. SEE (7) */
pa_sink_set_fixed_latency_within_thread(u->sink, i->sink->thread_info.fixed_latency);
/* (8.2) IF YOU NEED A FIXED BLOCK SIZE ROUND
* pa_sink_input_get_max_request(i) UP TO MULTIPLES OF IT
* HERE. SEE (6) */
pa_sink_set_max_request_within_thread(u->sink, pa_sink_input_get_max_request(i));
pa_sink_set_max_rewind_within_thread(u->sink, pa_sink_input_get_max_rewind(i));
@ -565,6 +584,8 @@ int pa__init(pa_module*m) {
u->sink_input->mute_changed = sink_input_mute_changed_cb;
u->sink_input->userdata = u;
/* (9) INITIALIZE ANYTHING ELSE YOU NEED HERE */
pa_sink_put(u->sink);
pa_sink_input_put(u->sink_input);