lavr: Use AV_SAMPLE_FMT_NONE to auto-select the internal sample format

Also make this the default value.

avplay.c

@@ -1948,8 +1948,6 @@ static int audio_decode_frame(VideoState *is, double *pts_ptr)
                     av_opt_set_int(is->avr, "out_channel_layout", is->sdl_channel_layout, 0);
                     av_opt_set_int(is->avr, "out_sample_fmt",     is->sdl_sample_fmt,     0);
                     av_opt_set_int(is->avr, "out_sample_rate",    dec->sample_rate,       0);
-                    if (av_get_bytes_per_sample(dec->sample_fmt) <= 2)
-                        av_opt_set_int(is->avr, "internal_sample_fmt", AV_SAMPLE_FMT_S16P, 0);
 
                     if ((ret = avresample_open(is->avr)) < 0) {
                         fprintf(stderr, "error initializing libavresample\n");

libavfilter/af_resample.c

@@ -102,12 +102,6 @@ static int config_output(AVFilterLink *outlink)
     av_opt_set_int(s->avr,  "in_sample_rate",    inlink ->sample_rate,    0);
     av_opt_set_int(s->avr, "out_sample_rate",    outlink->sample_rate,    0);
 
-    /* if both the input and output formats are s16 or u8, use s16 as
-       the internal sample format */
-    if (av_get_bytes_per_sample(inlink->format)  <= 2 &&
-        av_get_bytes_per_sample(outlink->format) <= 2)
-        av_opt_set_int(s->avr, "internal_sample_fmt", AV_SAMPLE_FMT_S16P, 0);
-
     if ((ret = avresample_open(s->avr)) < 0)
         return ret;
 

libavresample/options.c

@@ -39,7 +39,7 @@ static const AVOption options[] = {
     { "out_channel_layout",     "Output Channel Layout",    OFFSET(out_channel_layout),     AV_OPT_TYPE_INT64,  { 0                     }, INT64_MIN,            INT64_MAX,              PARAM },
     { "out_sample_fmt",         "Output Sample Format",     OFFSET(out_sample_fmt),         AV_OPT_TYPE_INT,    { AV_SAMPLE_FMT_S16     }, AV_SAMPLE_FMT_U8,     AV_SAMPLE_FMT_NB-1,     PARAM },
     { "out_sample_rate",        "Output Sample Rate",       OFFSET(out_sample_rate),        AV_OPT_TYPE_INT,    { 48000                 }, 1,                    INT_MAX,                PARAM },
-    { "internal_sample_fmt",    "Internal Sample Format",   OFFSET(internal_sample_fmt),    AV_OPT_TYPE_INT,    { AV_SAMPLE_FMT_FLTP    }, AV_SAMPLE_FMT_NONE,   AV_SAMPLE_FMT_NB-1,     PARAM },
+    { "internal_sample_fmt",    "Internal Sample Format",   OFFSET(internal_sample_fmt),    AV_OPT_TYPE_INT,    { AV_SAMPLE_FMT_NONE    }, AV_SAMPLE_FMT_NONE,   AV_SAMPLE_FMT_NB-1,     PARAM },
     { "mix_coeff_type",         "Mixing Coefficient Type",  OFFSET(mix_coeff_type),         AV_OPT_TYPE_INT,    { AV_MIX_COEFF_TYPE_FLT }, AV_MIX_COEFF_TYPE_Q8, AV_MIX_COEFF_TYPE_NB-1, PARAM, "mix_coeff_type" },
         { "q8",  "16-bit 8.8 Fixed-Point",   0, AV_OPT_TYPE_CONST, { AV_MIX_COEFF_TYPE_Q8  }, INT_MIN, INT_MAX, PARAM, "mix_coeff_type" },
         { "q15", "32-bit 17.15 Fixed-Point", 0, AV_OPT_TYPE_CONST, { AV_MIX_COEFF_TYPE_Q15 }, INT_MIN, INT_MAX, PARAM, "mix_coeff_type" },

libavresample/utils.c

@@ -57,18 +57,23 @@ int avresample_open(AVAudioResampleContext *avr)
     avr->resample_needed   = avr->in_sample_rate != avr->out_sample_rate ||
                              avr->force_resampling;
 
-    /* set sample format conversion parameters */
-    /* override user-requested internal format to avoid unexpected failures
-       TODO: support more internal formats */
-    if (avr->resample_needed && avr->internal_sample_fmt != AV_SAMPLE_FMT_S16P) {
-        av_log(avr, AV_LOG_WARNING, "Using s16p as internal sample format\n");
-        avr->internal_sample_fmt = AV_SAMPLE_FMT_S16P;
-    } else if (avr->mixing_needed &&
-               avr->internal_sample_fmt != AV_SAMPLE_FMT_S16P &&
-               avr->internal_sample_fmt != AV_SAMPLE_FMT_FLTP) {
-        av_log(avr, AV_LOG_WARNING, "Using fltp as internal sample format\n");
-        avr->internal_sample_fmt = AV_SAMPLE_FMT_FLTP;
+    /* select internal sample format if not specified by the user */
+    if (avr->internal_sample_fmt == AV_SAMPLE_FMT_NONE &&
+        (avr->mixing_needed || avr->resample_needed)) {
+        enum AVSampleFormat  in_fmt = av_get_planar_sample_fmt(avr->in_sample_fmt);
+        enum AVSampleFormat out_fmt = av_get_planar_sample_fmt(avr->out_sample_fmt);
+        int max_bps = FFMAX(av_get_bytes_per_sample(in_fmt),
+                            av_get_bytes_per_sample(out_fmt));
+        if (avr->resample_needed || max_bps <= 2) {
+            avr->internal_sample_fmt = AV_SAMPLE_FMT_S16P;
+        } else if (avr->mixing_needed) {
+            avr->internal_sample_fmt = AV_SAMPLE_FMT_FLTP;
+        }
+        av_log(avr, AV_LOG_DEBUG, "Using %s as internal sample format\n",
+               av_get_sample_fmt_name(avr->internal_sample_fmt));
     }
+
+    /* set sample format conversion parameters */
     if (avr->in_channels == 1)
         avr->in_sample_fmt = av_get_planar_sample_fmt(avr->in_sample_fmt);
     if (avr->out_channels == 1)