pcm-mpeg: improve log message wording

We support every defined value for channel layout, bitrate and sample depth.
All other values are not unsupported, but reserved.
Update comments to say "are used" instead of "are known or exist".
Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

libavcodec/pcm-mpeg.c

@@ -70,14 +70,14 @@ static int pcm_bluray_parse_header(AVCodecContext *avctx,
     /* get the sample depth and derive the sample format from it */
     avctx->bits_per_coded_sample = bits_per_samples[header[3] >> 6];
     if (!avctx->bits_per_coded_sample) {
-        av_log(avctx, AV_LOG_ERROR, "unsupported sample depth (0)\n");
+        av_log(avctx, AV_LOG_ERROR, "reserved sample depth (0)\n");
         return -1;
     }
     avctx->sample_fmt = avctx->bits_per_coded_sample == 16 ? AV_SAMPLE_FMT_S16 :
                                                              AV_SAMPLE_FMT_S32;
     avctx->bits_per_raw_sample = avctx->bits_per_coded_sample;
 
-    /* get the sample rate. Not all values are known or exist. */
+    /* get the sample rate. Not all values are used. */
     switch (header[2] & 0x0f) {
     case 1:
         avctx->sample_rate = 48000;
@@ -90,13 +90,13 @@ static int pcm_bluray_parse_header(AVCodecContext *avctx,
         break;
     default:
         avctx->sample_rate = 0;
-        av_log(avctx, AV_LOG_ERROR, "unsupported sample rate (%d)\n",
+        av_log(avctx, AV_LOG_ERROR, "reserved sample rate (%d)\n",
                header[2] & 0x0f);
         return -1;
     }
 
     /*
-     * get the channel number (and mapping). Not all values are known or exist.
+     * get the channel number (and mapping). Not all values are used.
      * It must be noted that the number of channels in the MPEG stream can
      * differ from the actual meaningful number, e.g. mono audio still has two
      * channels, one being empty.
@@ -104,7 +104,7 @@ static int pcm_bluray_parse_header(AVCodecContext *avctx,
     avctx->channel_layout  = channel_layouts[channel_layout];
     avctx->channels        =        channels[channel_layout];
     if (!avctx->channels) {
-        av_log(avctx, AV_LOG_ERROR, "unsupported channel configuration (%d)\n",
+        av_log(avctx, AV_LOG_ERROR, "reserved channel configuration (%d)\n",
                channel_layout);
         return -1;
     }