[FFmpeg-devel] [PATCH] lavfi/volume: implement process_command() callback, with the volume command

[Stefano Sabatini]

Address trac ticket #2868.

TODO: bump micro
---
 doc/filters.texi        | 13 +++++++++++++
 libavfilter/af_volume.c | 27 +++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/doc/filters.texi b/doc/filters.texi
index d29bedc..7d2d73a 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -1868,6 +1868,19 @@ Note that when @option{eval} is set to @samp{init} only the
 @var{sample_rate} and @var{tb} variables are available, all other
 variables will evaluate to NAN.
 
+ at subsection Commands
+
+This filter supports the following commands:
+ at table @option
+ at item volume
+
+Modify the volume expression.
+The command accepts the same syntax of the corresponding option.
+
+If the specified expression is not valid, it is kept at its current
+value.
+ at end table
+
 @subsection Examples
 
 @itemize
diff --git a/libavfilter/af_volume.c b/libavfilter/af_volume.c
index 9bfd840..fbeb84c 100644
--- a/libavfilter/af_volume.c
+++ b/libavfilter/af_volume.c
@@ -298,6 +298,32 @@ static int config_output(AVFilterLink *outlink)
     return 0;
 }
 
+static int process_command(AVFilterContext *ctx, const char *cmd, const char *args,
+                           char *res, int res_len, int flags)
+{
+    VolumeContext *vol = ctx->priv;
+    int ret;
+
+    if (!strcmp(cmd, "volume"))
+        ret = set_expr(&vol->volume_pexpr, args, ctx);
+    else
+        ret = AVERROR(ENOSYS);
+
+    if (ret < 0)
+        return ret;
+
+    if (vol->eval_mode == EVAL_MODE_INIT) {
+        vol->volume = av_expr_eval(vol->volume_pexpr, vol->var_values, NULL);
+        if (isnan(vol->volume)) {
+            av_log(ctx, AV_LOG_ERROR, "Invalid value NaN for volume, setting value to 0\n");
+            vol->volume = 0;
+        }
+        set_volume(ctx);
+    }
+
+    return 0;
+}
+
 #define D2TS(d)  (isnan(d) ? AV_NOPTS_VALUE : (int64_t)(d))
 #define TS2D(ts) ((ts) == AV_NOPTS_VALUE ? NAN : (double)(ts))
 #define TS2T(ts, tb) ((ts) == AV_NOPTS_VALUE ? NAN : (double)(ts)*av_q2d(tb))
@@ -429,4 +455,5 @@ AVFilter ff_af_volume = {
     .inputs         = avfilter_af_volume_inputs,
     .outputs        = avfilter_af_volume_outputs,
     .flags          = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
+    .process_command = process_command,
 };
-- 
1.8.1.2