app_mp3: Use correct buffer size and the same sample rate as the channel

Previously, the buffer used for MP3 streamed from HTTP servers had a size of
1 MB. For 8 kHz mono audio at 16 bit resolution, such a buffer covers about 1
minute. Only when the buffer is full does audio start to play.
For MP3 files streamed from a server, that is usually not a big deal as long as
the connection to the server is fast enough to supply that much data within a
second or two. For MP3 live streams however, it takes 1 minute to download 1
minute of audio, so without this change, app_mp3 wasn't really usable for MP3
live streams.
This commit changes the buffer size so that it covers 6 seconds of an MP3 file
streamed from a server and 0.5 seconds of an MP3 live stream. The latter is
identified by the use of a .m3u file extension.

app_mp3 so far only supported 8 kHz audio.
Now it always runs at the sample rate of the channel.

ASTERISK-26085 #close

Change-Id: Id1ee274733cd804a0edecf7450329b72f1235af0

diff --git a/apps/app_mp3.c b/apps/app_mp3.c
index 463a91906f849cf3ebeed1b773655aa07bf88acf..81ece8f2bb758c1fbd81601a4d7a7750765f09bd 100644 (file)
--- a/apps/app_mp3.c
+++ b/apps/app_mp3.c
@@ -47,6 +47,7 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #include "asterisk/module.h"
 #include "asterisk/translate.h"
 #include "asterisk/app.h"
+#include "asterisk/format.h"
 
 #define LOCAL_MPG_123 "/usr/local/bin/mpg123"
 #define MPG_123 "/usr/bin/mpg123"
@@ -76,9 +77,10 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
  ***/
 static char *app = "MP3Player";
 
-static int mp3play(const char *filename, int fd)
+static int mp3play(const char *filename, unsigned int sampling_rate, int fd)
 {
        int res;
+       char sampling_rate_str[8];
 
        res = ast_safe_fork(0);
        if (res < 0) 
@@ -92,30 +94,44 @@ static int mp3play(const char *filename, int fd)
        dup2(fd, STDOUT_FILENO);
        ast_close_fds_above_n(STDERR_FILENO);
 
+       snprintf(sampling_rate_str, 8, "%u", sampling_rate);
+
        /* Execute mpg123, but buffer if it's a net connection */
-       if (!strncasecmp(filename, "http://", 7)) {
+       if (!strncasecmp(filename, "http://", 7) && strstr(filename, ".m3u")) {
+           char buffer_size_str[8];
+           snprintf(buffer_size_str, 8, "%u", (int) 0.5*2*sampling_rate/1000); // 0.5 seconds for a live stream
+               /* Most commonly installed in /usr/local/bin */
+           execl(LOCAL_MPG_123, "mpg123", "-q", "-s", "-b", buffer_size_str, "-f", "8192", "--mono", "-r", sampling_rate_str, "-@", filename, (char *)NULL);
+               /* But many places has it in /usr/bin */
+           execl(MPG_123, "mpg123", "-q", "-s", "-b", buffer_size_str, "-f", "8192", "--mono", "-r", sampling_rate_str, "-@", filename, (char *)NULL);
+               /* As a last-ditch effort, try to use PATH */
+           execlp("mpg123", "mpg123", "-q", "-s", "-b", buffer_size_str, "-f", "8192", "--mono", "-r", sampling_rate_str, "-@", filename, (char *)NULL);
+       }
+       else if (!strncasecmp(filename, "http://", 7)) {
+           char buffer_size_str[8];
+           snprintf(buffer_size_str, 8, "%u", 6*2*sampling_rate/1000); // 6 seconds for a remote MP3 file
                /* Most commonly installed in /usr/local/bin */
-           execl(LOCAL_MPG_123, "mpg123", "-q", "-s", "-b", "1024", "-f", "8192", "--mono", "-r", "8000", filename, (char *)NULL);
+           execl(LOCAL_MPG_123, "mpg123", "-q", "-s", "-b", buffer_size_str, "-f", "8192", "--mono", "-r", sampling_rate_str, filename, (char *)NULL);
                /* But many places has it in /usr/bin */
-           execl(MPG_123, "mpg123", "-q", "-s", "-b", "1024","-f", "8192", "--mono", "-r", "8000", filename, (char *)NULL);
+           execl(MPG_123, "mpg123", "-q", "-s", "-b", buffer_size_str, "-f", "8192", "--mono", "-r", sampling_rate_str, filename, (char *)NULL);
                /* As a last-ditch effort, try to use PATH */
-           execlp("mpg123", "mpg123", "-q", "-s", "-b", "1024",  "-f", "8192", "--mono", "-r", "8000", filename, (char *)NULL);
+           execlp("mpg123", "mpg123", "-q", "-s", "-b", buffer_size_str, "-f", "8192", "--mono", "-r", sampling_rate_str, filename, (char *)NULL);
        }
        else if (strstr(filename, ".m3u")) {
                /* Most commonly installed in /usr/local/bin */
-           execl(LOCAL_MPG_123, "mpg123", "-q", "-z", "-s", "-b", "1024", "-f", "8192", "--mono", "-r", "8000", "-@", filename, (char *)NULL);
+           execl(LOCAL_MPG_123, "mpg123", "-q", "-z", "-s", "-f", "8192", "--mono", "-r", sampling_rate_str, "-@", filename, (char *)NULL);
                /* But many places has it in /usr/bin */
-           execl(MPG_123, "mpg123", "-q", "-z", "-s", "-b", "1024","-f", "8192", "--mono", "-r", "8000", "-@", filename, (char *)NULL);
+           execl(MPG_123, "mpg123", "-q", "-z", "-s", "-f", "8192", "--mono", "-r", sampling_rate_str, "-@", filename, (char *)NULL);
                /* As a last-ditch effort, try to use PATH */
-           execlp("mpg123", "mpg123", "-q", "-z", "-s", "-b", "1024",  "-f", "8192", "--mono", "-r", "8000", "-@", filename, (char *)NULL);
+           execlp("mpg123", "mpg123", "-q", "-z", "-s",  "-f", "8192", "--mono", "-r", sampling_rate_str, "-@", filename, (char *)NULL);
        }
        else {
                /* Most commonly installed in /usr/local/bin */
-           execl(MPG_123, "mpg123", "-q", "-s", "-f", "8192", "--mono", "-r", "8000", filename, (char *)NULL);
+           execl(MPG_123, "mpg123", "-q", "-s", "-f", "8192", "--mono", "-r", sampling_rate_str, filename, (char *)NULL);
                /* But many places has it in /usr/bin */
-           execl(LOCAL_MPG_123, "mpg123", "-q", "-s", "-f", "8192", "--mono", "-r", "8000", filename, (char *)NULL);
+           execl(LOCAL_MPG_123, "mpg123", "-q", "-s", "-f", "8192", "--mono", "-r", sampling_rate_str, filename, (char *)NULL);
                /* As a last-ditch effort, try to use PATH */
-           execlp("mpg123", "mpg123", "-q", "-s", "-f", "8192", "--mono", "-r", "8000", filename, (char *)NULL);
+           execlp("mpg123", "mpg123", "-q", "-s", "-f", "8192", "--mono", "-r", sampling_rate_str, filename, (char *)NULL);
        }
        /* Can't use ast_log since FD's are closed */
        fprintf(stderr, "Execute of mpg123 failed\n");
@@ -154,6 +170,9 @@ static int mp3_exec(struct ast_channel *chan, const char *data)
        } myf = {
                .f = { 0, },
        };
+       struct ast_format native_format;
+       unsigned int sampling_rate;
+       enum ast_format_id write_format;
 
        ast_format_clear(&owriteformat);
        if (ast_strlen_zero(data)) {
@@ -168,14 +187,18 @@ static int mp3_exec(struct ast_channel *chan, const char *data)
        
        ast_stopstream(chan);
 
+       ast_best_codec(ast_channel_nativeformats(chan), &native_format);
+       sampling_rate = ast_format_rate(&native_format);
+       write_format = ast_format_slin_by_rate(sampling_rate);
+
        ast_format_copy(&owriteformat, ast_channel_writeformat(chan));
-       res = ast_set_write_format_by_id(chan, AST_FORMAT_SLINEAR);
+       res = ast_set_write_format_by_id(chan, write_format);
        if (res < 0) {
                ast_log(LOG_WARNING, "Unable to set write format to signed linear\n");
                return -1;
        }
        
-       res = mp3play(data, fds[1]);
+       res = mp3play(data, sampling_rate, fds[1]);
        if (!strncasecmp(data, "http://", 7)) {
                timeout = 10000;
        }
@@ -192,7 +215,7 @@ static int mp3_exec(struct ast_channel *chan, const char *data)
                                res = timed_read(fds[0], myf.frdata, sizeof(myf.frdata), timeout);
                                if (res > 0) {
                                        myf.f.frametype = AST_FRAME_VOICE;
-                                       ast_format_set(&myf.f.subclass.format, AST_FORMAT_SLINEAR, 0);
+                                       ast_format_set(&myf.f.subclass.format, write_format, 0);
                                        myf.f.datalen = res;
                                        myf.f.samples = res / 2;
                                        myf.f.mallocd = 0;
@@ -210,7 +233,7 @@ static int mp3_exec(struct ast_channel *chan, const char *data)
                                        res = 0;
                                        break;
                                }
-                               next = ast_tvadd(next, ast_samp2tv(myf.f.samples, 8000));
+                               next = ast_tvadd(next, ast_samp2tv(myf.f.samples, sampling_rate));
                        } else {
                                ms = ast_waitfor(chan, ms);
                                if (ms < 0) {