avcodec: add av_get_exact_bits_per_sample() function

This only returns bits per sample when it is exactly correct. That is, the
codec contains only raw samples with no frame headers or padding. This applies
to basically all PCM codecs and a small subset of ADPCM codecs.

libavcodec/avcodec.h

@@ -3932,6 +3932,16 @@ void avcodec_default_free_buffers(AVCodecContext *s);
  */
 int av_get_bits_per_sample(enum CodecID codec_id);
 
+/**
+ * Return codec bits per sample.
+ * Only return non-zero if the bits per sample is exactly correct, not an
+ * approximation.
+ *
+ * @param[in] codec_id the codec
+ * @return Number of bits per sample or zero if unknown for the given codec.
+ */
+int av_get_exact_bits_per_sample(enum CodecID codec_id);
+
 /* frame parsing */
 typedef struct AVCodecParserContext {
     void *priv_data;

libavcodec/utils.c

@@ -1681,21 +1681,15 @@ void avcodec_default_free_buffers(AVCodecContext *avctx)
     }
 }
 
-int av_get_bits_per_sample(enum CodecID codec_id){
+int av_get_exact_bits_per_sample(enum CodecID codec_id)
+{
     switch(codec_id){
-    case CODEC_ID_ADPCM_SBPRO_2:
-        return 2;
-    case CODEC_ID_ADPCM_SBPRO_3:
-        return 3;
-    case CODEC_ID_ADPCM_SBPRO_4:
     case CODEC_ID_ADPCM_CT:
     case CODEC_ID_ADPCM_IMA_APC:
-    case CODEC_ID_ADPCM_IMA_WAV:
-    case CODEC_ID_ADPCM_IMA_QT:
-    case CODEC_ID_ADPCM_SWF:
-    case CODEC_ID_ADPCM_MS:
-    case CODEC_ID_ADPCM_YAMAHA:
+    case CODEC_ID_ADPCM_IMA_EA_SEAD:
+    case CODEC_ID_ADPCM_IMA_WS:
     case CODEC_ID_ADPCM_G722:
+    case CODEC_ID_ADPCM_YAMAHA:
         return 4;
     case CODEC_ID_PCM_ALAW:
     case CODEC_ID_PCM_MULAW:
@@ -1730,6 +1724,24 @@ int av_get_bits_per_sample(enum CodecID codec_id){
     }
 }
 
+int av_get_bits_per_sample(enum CodecID codec_id)
+{
+    switch (codec_id) {
+    case CODEC_ID_ADPCM_SBPRO_2:
+        return 2;
+    case CODEC_ID_ADPCM_SBPRO_3:
+        return 3;
+    case CODEC_ID_ADPCM_SBPRO_4:
+    case CODEC_ID_ADPCM_IMA_WAV:
+    case CODEC_ID_ADPCM_IMA_QT:
+    case CODEC_ID_ADPCM_SWF:
+    case CODEC_ID_ADPCM_MS:
+        return 4;
+    default:
+        return av_get_exact_bits_per_sample(codec_id);
+    }
+}
+
 #if !HAVE_THREADS
 int ff_thread_init(AVCodecContext *s){
     return -1;