19_audio_volume_adj.patch by (Calcium | calcium nurs or jp)

Originally committed as revision 4065 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -254,6 +254,7 @@ static char *video_standard = "ntsc";
 
 static char *audio_grab_format = "audio_device";
 static char *audio_device = NULL;
+static int audio_volume = 100; //
 
 static int using_stdin = 0;
 static int using_vhook = 0;
@@ -1209,6 +1210,21 @@ static int output_packet(AVInputStream *ist, int ist_index,
                                         &buffer_to_free);
             }
 
+            // preprocess audio (volume)
+            if (ist->st->codec.codec_type == CODEC_TYPE_AUDIO) {
+                if (audio_volume != 100) {
+                    short *volp;
+                    int v;
+                    volp = samples;
+                    for(i=0;i<(data_size / sizeof(short));i++) {
+                        v = (*volp) * audio_volume / 100;
+                        if (v < -32768) v = -32768;
+                        if (v >  32767) v = 32767;
+                        *volp++ = v;
+                    }
+                }
+            }
+
             /* frame rate emulation */
             if (ist->st->codec.rate_emu) {
                 int64_t pts = av_rescale((int64_t) ist->frame * ist->st->codec.frame_rate_base, 1000000, ist->st->codec.frame_rate);
@@ -4075,6 +4091,7 @@ const OptionDef options[] = {
     { "an", OPT_BOOL | OPT_AUDIO, {(void*)&audio_disable}, "disable audio" },
     { "acodec", HAS_ARG | OPT_AUDIO, {(void*)opt_audio_codec}, "force audio codec ('copy' to copy stream)", "codec" },
     { "atag", HAS_ARG | OPT_EXPERT | OPT_AUDIO, {(void*)opt_audio_tag}, "force audio tag/fourcc", "fourcc/tag" },
+    { "vol", OPT_INT | HAS_ARG | OPT_AUDIO, {(void*)&audio_volume}, "change audio volume (100=normal)" , "volume" }, //
 
     /* grab options */
     { "vd", HAS_ARG | OPT_EXPERT | OPT_VIDEO | OPT_GRAB, {(void*)opt_video_device}, "set video grab device", "device" },