libswresample: introduce int swr_set_compensation() instead of void swr_compensate()

The new version returns AVERROR(EINVAL) is the specified paramters are invalid,
and also creates the resampler if none was used so far.
Signed-off-by: Marton Balint <cus@passwd.hu>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

ffmpeg.c

@@ -1160,7 +1160,7 @@ need_realloc:
                 av_log(NULL, AV_LOG_VERBOSE, "compensating audio timestamp drift:%f compensation:%d in:%d\n",
                        delta, comp, enc->sample_rate);
 //                fprintf(stderr, "drift:%f len:%d opts:%"PRId64" ipts:%"PRId64" fifo:%d\n", delta, -1, ost->sync_opts, (int64_t)(get_sync_ipts(ost) * enc->sample_rate), av_fifo_size(ost->fifo)/(ost->st->codec->channels * 2));
-                swr_compensate(ost->swr, comp, enc->sample_rate);
+                swr_set_compensation(ost->swr, comp, enc->sample_rate);
             }
         }
     } else

libswresample/resample.c

@@ -245,11 +245,27 @@ void swri_resample_free(ResampleContext **c){
     av_freep(c);
 }
 
-void swr_compensate(struct SwrContext *s, int sample_delta, int compensation_distance){
-    ResampleContext *c= s->resample;
-//    sample_delta += (c->ideal_dst_incr - c->dst_incr)*(int64_t)c->compensation_distance / c->ideal_dst_incr;
+int swr_set_compensation(struct SwrContext *s, int sample_delta, int compensation_distance){
+    ResampleContext *c;
+    int ret;
+
+    if (!s || compensation_distance < 0)
+        return AVERROR(EINVAL);
+    if (!compensation_distance && sample_delta)
+        return AVERROR(EINVAL);
+    if (!s->resample) {
+        s->flags |= SWR_FLAG_RESAMPLE;
+        ret = swr_init(s);
+        if (ret < 0)
+            return ret;
+    }
+    c= s->resample;
     c->compensation_distance= compensation_distance;
-    c->dst_incr = c->ideal_dst_incr - c->ideal_dst_incr * (int64_t)sample_delta / compensation_distance;
+    if (compensation_distance)
+        c->dst_incr = c->ideal_dst_incr - c->ideal_dst_incr * (int64_t)sample_delta / compensation_distance;
+    else
+        c->dst_incr = c->ideal_dst_incr;
+    return 0;
 }
 
 int swri_resample(ResampleContext *c, int16_t *dst, const int16_t *src, int *consumed, int src_size, int dst_size, int update_ctx){

libswresample/swresample.h

@@ -30,7 +30,7 @@
 #include "libavutil/samplefmt.h"
 
 #define LIBSWRESAMPLE_VERSION_MAJOR 0
-#define LIBSWRESAMPLE_VERSION_MINOR 5
+#define LIBSWRESAMPLE_VERSION_MINOR 6
 #define LIBSWRESAMPLE_VERSION_MICRO 100
 
 #define LIBSWRESAMPLE_VERSION_INT  AV_VERSION_INT(LIBSWRESAMPLE_VERSION_MAJOR, \
@@ -114,7 +114,7 @@ int swr_convert(struct SwrContext *s, uint8_t *out[SWR_CH_MAX], int out_count,
 /**
  * Activate resampling compensation.
  */
-void swr_compensate(struct SwrContext *s, int sample_delta, int compensation_distance);
+int swr_set_compensation(struct SwrContext *s, int sample_delta, int compensation_distance);
 
 /**
  * Set a customized input channel mapping.