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audiohook.c: Substitute silence for unavailable audio frames

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There are 4 scenarios to consider when capturing audio from a channel
with an audiohook:

 1. There is no rx and no tx audio, so return nothing.
 2. There is rx but no tx audio, so return rx.
 3. There is tx but no rx audio, so return tx.
 4. There is rx and tx audio, so mix them and return.

The file passed as the primary argument to MixMonitor will be written to
in scenarios 2, 3, and 4. However, if you pass the r() and t() options
to MixMonitor, a frame will only be written to the r() file if there was
rx audio and a frame will only be written to the t() file if there was
tx audio.

If you subsequently take the r() and t() files and try to mix them, the
sides of the conversation will 'drift' and be non-representative of the
user experience.

This patch adds a new 'S' option to MixMonitor that injects a frame of
silence on either the r() side or the t() side of the channel so that
when later mixed, there is no such drift.

Change-Id: Ibf5ed73a811087727bd561a89a59f4447b4ee20e
This commit is contained in:
Sean Bright
2019-08-09 16:53:03 -04:00
parent 15624d9a7a
commit 64906c4c9b
4 changed files with 32 additions and 1 deletions
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13
apps/app_mixmonitor.c
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@@ -115,6 +115,11 @@
Like with the basic filename argument, if an absolute path isn't given, it will create
the file in the configured monitoring directory.</para>
</option>
<option name="S">
<para>When combined with the <replaceable>r</replaceable> or <replaceable>t</replaceable>
option, inserts silence when necessary to maintain synchronization between the receive
and transmit audio streams.</para>
</option>
<option name="i">
<argument name="chanvar" required="true" />
<para>Stores the MixMonitor's ID on this channel variable.</para>
@@ -347,7 +352,8 @@ enum mixmonitor_flags {
MUXFLAG_VMRECIPIENTS = (1 << 10),
MUXFLAG_BEEP = (1 << 11),
MUXFLAG_BEEP_START = (1 << 12),
MUXFLAG_BEEP_STOP = (1 << 13)
MUXFLAG_BEEP_STOP = (1 << 13),
MUXFLAG_RWSYNC = (1 << 14),
};
enum mixmonitor_args {
@@ -359,6 +365,7 @@ enum mixmonitor_args {
OPT_ARG_UID,
OPT_ARG_VMRECIPIENTS,
OPT_ARG_BEEP_INTERVAL,
OPT_ARG_RWSYNC,
OPT_ARG_ARRAY_SIZE, /* Always last element of the enum */
};
@@ -375,6 +382,7 @@ AST_APP_OPTIONS(mixmonitor_opts, {
AST_APP_OPTION_ARG('t', MUXFLAG_WRITE, OPT_ARG_WRITENAME),
AST_APP_OPTION_ARG('i', MUXFLAG_UID, OPT_ARG_UID),
AST_APP_OPTION_ARG('m', MUXFLAG_VMRECIPIENTS, OPT_ARG_VMRECIPIENTS),
AST_APP_OPTION_ARG('S', MUXFLAG_RWSYNC, OPT_ARG_RWSYNC),
});
struct mixmonitor_ds {
@@ -962,6 +970,9 @@ static int launch_monitor_thread(struct ast_channel *chan, const char *filename,
}
ast_set_flag(&mixmonitor->audiohook, AST_AUDIOHOOK_TRIGGER_SYNC);
if ((ast_test_flag(mixmonitor, MUXFLAG_RWSYNC))) {
ast_set_flag(&mixmonitor->audiohook, AST_AUDIOHOOK_SUBSTITUTE_SILENCE);
}
if (readvol)
mixmonitor->audiohook.options.read_volume = readvol;