[pulseaudio-discuss] [PATCH 2/2] pacat: Use a ringbuffer for playback mode
Ahmed S. Darwish
darwish.07 at gmail.com
Mon Nov 28 04:01:21 UTC 2016
Current pacat code reads whatever available from STDIN and writes
it directly to the playback stream. A minimal buffer is created
for each read operation; no further reads are then allowed unless
earlier read buffer has been fully consumed by a stream write.
While quite simple, this model breaks upon the new requirements of
writing only frame-aligned data to the stream (commits #1 and #2).
The kernel read syscall can return a length much smaller than the
frame-aligned size requested, leading to invalid unaligned writes.
This can easily be reproduced by choosing a starved STDIN backend:
pacat /dev/random pa_stream_write() failed: EINVAL
echo 1234 | pacat pa_stream_write() failed: EINVAL
So guard against incomplete kernel reads by using a ringbuffer.
Meanwhile leave the simple recording mode buffering as is: it just
writes to plain STDOUT without any special needs.
CommitReference #1: 22827a5e1e62
CommitReference #2: 150ace90f380
BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=98475
BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=77595
Signed-off-by: Ahmed S. Darwish <darwish.07 at gmail.com>
---
src/utils/pacat.c | 89 +++++++++++++++++++++++++++++++++++--------------------
1 file changed, 57 insertions(+), 32 deletions(-)
diff --git a/src/utils/pacat.c b/src/utils/pacat.c
index 68362ec..39c002e 100644
--- a/src/utils/pacat.c
+++ b/src/utils/pacat.c
@@ -38,10 +38,12 @@
#include <pulse/pulseaudio.h>
#include <pulse/rtclock.h>
+#include <pulsecore/atomic.h>
#include <pulsecore/core-util.h>
#include <pulsecore/i18n.h>
#include <pulsecore/log.h>
#include <pulsecore/macro.h>
+#include <pulsecore/ringbuffer.h>
#include <pulsecore/sndfile-util.h>
#include <pulsecore/sample-util.h>
@@ -56,6 +58,11 @@ static pa_context *context = NULL;
static pa_stream *stream = NULL;
static pa_mainloop_api *mainloop_api = NULL;
+/* Ring buffer for playback mode */
+static pa_ringbuffer ringbuffer = { 0, };
+static pa_atomic_t rb_count = PA_ATOMIC_INIT(0);
+
+/* Flat buffer for recording mode */
static void *buffer = NULL;
static size_t buffer_length = 0, buffer_index = 0;
@@ -155,29 +162,35 @@ static void start_drain(void) {
/* Write some data to the stream */
static void do_stream_write(size_t length) {
- size_t l;
- pa_assert(length);
+ int rb_freelen;
+ void *buf;
+ size_t w;
- if (!buffer || !buffer_length)
+ if (!ringbuffer.memory)
return;
- l = length;
- if (l > buffer_length)
- l = buffer_length;
+ while (length > 0) {
- if (pa_stream_write(stream, (uint8_t*) buffer + buffer_index, l, NULL, 0, PA_SEEK_RELATIVE) < 0) {
- pa_log(_("pa_stream_write() failed: %s"), pa_strerror(pa_context_errno(context)));
- quit(1);
- return;
- }
+ buf = pa_ringbuffer_peek(&ringbuffer, &rb_freelen);
- buffer_length -= l;
- buffer_index += l;
+ /* Frame-align our audio packets or the server will happily ignore
+ * them upon arrival. Also only write as much data as requested: do
+ * not overflow the stream by emptying the whole ringbuffer. */
+ w = PA_MIN(pa_frame_align(length, &sample_spec),
+ pa_frame_align(rb_freelen, &sample_spec));
+ if (!w)
+ break;
- if (!buffer_length) {
- pa_xfree(buffer);
- buffer = NULL;
- buffer_index = buffer_length = 0;
+ if (pa_stream_write(stream, buf, w, NULL, 0, PA_SEEK_RELATIVE) < 0) {
+ pa_log(_("pa_stream_write() failed: %s"), pa_strerror(pa_context_errno(context)));
+ quit(1);
+ return;
+ }
+
+ pa_ringbuffer_drop(&ringbuffer, w);
+
+ pa_assert(w <= length);
+ length -= w;
}
}
@@ -192,9 +205,6 @@ static void stream_write_callback(pa_stream *s, size_t length, void *userdata) {
if (stdio_event)
mainloop_api->io_enable(stdio_event, PA_IO_EVENT_INPUT);
- if (!buffer)
- return;
-
do_stream_write(length);
} else {
@@ -540,25 +550,42 @@ fail:
/* New data on STDIN **/
static void stdin_callback(pa_mainloop_api*a, pa_io_event *e, int fd, pa_io_event_flags_t f, void *userdata) {
- size_t l, w = 0;
- ssize_t r;
- bool stream_not_ready;
+ int rb_freelen;
+ void *buf;
+ size_t writable, r;
pa_assert(a == mainloop_api);
pa_assert(e);
pa_assert(stdio_event == e);
- stream_not_ready = !stream || pa_stream_get_state(stream) != PA_STREAM_READY ||
- !(l = w = pa_stream_writable_size(stream));
+ /* Stream not ready? */
+ if (!stream || pa_stream_get_state(stream) != PA_STREAM_READY ||
+ !(writable = pa_stream_writable_size(stream))) {
- if (buffer || stream_not_ready) {
mainloop_api->io_enable(stdio_event, PA_IO_EVENT_NULL);
return;
}
- buffer = pa_xmalloc(l);
+ /* Ring APIs forces us to use integers: ensure safe casting */
+ writable = PA_MIN(writable, (size_t)INT_MAX);
+
+ if (!ringbuffer.memory) {
+ size_t rb_size = PA_MAX(writable, 4096 * pa_frame_size(&sample_spec));
+ ringbuffer.memory = pa_xmalloc(rb_size);
+ ringbuffer.capacity = rb_size;
+ ringbuffer.count = &rb_count;
+ }
+
+ buf = pa_ringbuffer_begin_write(&ringbuffer, &rb_freelen);
+
+ if (!rb_freelen) {
+ do_stream_write(writable);
+ return;
+ }
- if ((r = pa_read(fd, buffer, l, userdata)) <= 0) {
+ /* Avoid underruns due to a too-long read(): read only what the
+ * stream requested and don't try to fill the whole ringbuffer. */
+ if ((r = pa_read(fd, buf, PA_MIN((int) writable, rb_freelen), userdata)) <= 0) {
if (r == 0) {
if (verbose)
pa_log(_("Got EOF."));
@@ -575,11 +602,9 @@ static void stdin_callback(pa_mainloop_api*a, pa_io_event *e, int fd, pa_io_even
return;
}
- buffer_length = (uint32_t) r;
- buffer_index = 0;
+ pa_ringbuffer_end_write(&ringbuffer, r);
- if (w)
- do_stream_write(w);
+ do_stream_write(writable);
}
/* Some data may be written to STDOUT */
--
Darwish
http://darwish.chasingpointers.com
More information about the pulseaudio-discuss
mailing list