audiohooks: Remove redundant codec translations when using audiohooks

The main frame read and write handlers in main/channel.c don't use the
optimum placement in the processing flow for calling audiohooks
callbacks, as far as codec translation is concerned. This change places
the audiohooks callback code:
 * After the channel read translation if the frame is not linear before
the translation, thereby increasing the chance that the frame is linear
as required by audiohooks
 * Before the channel write translation if the frame is linear at this
point
This prevents the audiohooks code from instantiating additional
translation paths to/from linear where a linear frame format is already
available, saving valuable CPU cycles

ASTERISK-26419

Change-Id: I6edd5771f0740e758e7eb42558b953f046c01f8f

diff --git a/main/channel.c b/main/channel.c
index f3f79399fe4547a25cff35479fe2a0a4d1bc5943..c6cb925b8c20c4637c95614db19b6924c09d5bcb 100644 (file)
--- a/main/channel.c
+++ b/main/channel.c
@@ -3914,6 +3914,7 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio)
                struct ast_frame *readq_tail = AST_LIST_LAST(ast_channel_readq(chan));
                struct ast_control_read_action_payload *read_action_payload;
                struct ast_party_connected_line connected;
+               int hooked = 0;
 
                /* if the channel driver returned more than one frame, stuff the excess
                   into the readq for the next ast_read call
@@ -4191,15 +4192,22 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio)
                                        break;
                                }
                        }
-                       /* Send frame to audiohooks if present */
-                       if (ast_channel_audiohooks(chan)) {
+                       /*
+                        * Send frame to audiohooks if present, if frametype is linear, to preserve
+                        * functional compatibility with previous behavior. If not linear, hold off
+                        * until transcoding is done where we are more likely to have a linear frame
+                        */
+                       if (ast_channel_audiohooks(chan) && ast_format_cache_is_slinear(f->subclass.format)) {
+                               /* Place hooked after declaration */
                                struct ast_frame *old_frame = f;
+                               hooked = 1;
 
                                f = ast_audiohook_write_list(chan, ast_channel_audiohooks(chan), AST_AUDIOHOOK_DIRECTION_READ, f);
                                if (old_frame != f) {
                                        ast_frfree(old_frame);
                                }
                        }
+
                        if (ast_channel_monitor(chan) && ast_channel_monitor(chan)->read_stream) {
                                /* XXX what does this do ? */
 #ifndef MONITOR_CONSTANT_DELAY
@@ -4242,6 +4250,16 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio)
                                }
                        }
 
+                       /* Second chance at hooking a linear frame, also the last chance */
+                       if (ast_channel_audiohooks(chan) && !hooked) {
+                               struct ast_frame *old_frame = f;
+
+                               f = ast_audiohook_write_list(chan, ast_channel_audiohooks(chan), AST_AUDIOHOOK_DIRECTION_READ, f);
+                               if (old_frame != f) {
+                                       ast_frfree(old_frame);
+                               }
+                       }
+
                        /*
                         * It is possible for the translation process on the channel to have
                         * produced multiple frames from the single input frame we passed it; if
@@ -5032,6 +5050,7 @@ int ast_write(struct ast_channel *chan, struct ast_frame *fr)
        int res = -1;
        struct ast_frame *f = NULL;
        int count = 0;
+       int hooked = 0;
 
        /*Deadlock avoidance*/
        while(ast_channel_trylock(chan)) {
@@ -5149,6 +5168,22 @@ int ast_write(struct ast_channel *chan, struct ast_frame *fr)
                        apply_plc(chan, fr);
                }
 
+               /*
+                * Send frame to audiohooks if present, if frametype is linear (else, later as per
+                * previous behavior)
+                */
+               if (ast_channel_audiohooks(chan)) {
+                       if (ast_format_cache_is_slinear(fr->subclass.format)) {
+                               struct ast_frame *old_frame;
+                               hooked = 1;
+                               old_frame = fr;
+                               fr = ast_audiohook_write_list(chan, ast_channel_audiohooks(chan), AST_AUDIOHOOK_DIRECTION_WRITE, fr);
+                               if (old_frame != fr) {
+                                       ast_frfree(old_frame);
+                               }
+                       }
+               }
+
                /* If the frame is in the raw write format, then it's easy... just use the frame - otherwise we will have to translate */
                if (ast_format_cmp(fr->subclass.format, ast_channel_rawwriteformat(chan)) == AST_FORMAT_CMP_EQUAL) {
                        f = fr;
@@ -5186,7 +5221,7 @@ int ast_write(struct ast_channel *chan, struct ast_frame *fr)
                        break;
                }
 
-               if (ast_channel_audiohooks(chan)) {
+               if (ast_channel_audiohooks(chan) && !hooked) {
                        struct ast_frame *prev = NULL, *new_frame, *cur, *dup;
                        int freeoldlist = 0;