avcodec: add av_get_audio_frame_duration() function.

This is a utility function for the user to get the frame duration based on
the codec id, frame size in bytes, and various AVCodecContext parameters.

doc/APIchanges

@@ -12,6 +12,10 @@ libavutil:   2011-04-18
 
 API changes, most recent first:
 
+2012-xx-xx - lavc 54.8.0
+  xxxxxxx Add av_get_exact_bits_per_sample()
+  xxxxxxx Add av_get_audio_frame_duration()
+
 2012-03-xx - xxxxxxx - lavc 54.7.0 - avcodec.h
   Add av_codec_is_encoder/decoder().
 

libavcodec/avcodec.h

@@ -3942,6 +3942,16 @@ int av_get_bits_per_sample(enum CodecID codec_id);
  */
 int av_get_exact_bits_per_sample(enum CodecID codec_id);
 
+/**
+ * Return audio frame duration.
+ *
+ * @param avctx        codec context
+ * @param frame_bytes  size of the frame, or 0 if unknown
+ * @return             frame duration, in samples, if known. 0 if not able to
+ *                     determine.
+ */
+int av_get_audio_frame_duration(AVCodecContext *avctx, int frame_bytes);
+
 /* frame parsing */
 typedef struct AVCodecParserContext {
     void *priv_data;

libavcodec/utils.c

@@ -1742,6 +1742,148 @@ int av_get_bits_per_sample(enum CodecID codec_id)
     }
 }
 
+int av_get_audio_frame_duration(AVCodecContext *avctx, int frame_bytes)
+{
+    int id, sr, ch, ba, tag, bps;
+
+    id  = avctx->codec_id;
+    sr  = avctx->sample_rate;
+    ch  = avctx->channels;
+    ba  = avctx->block_align;
+    tag = avctx->codec_tag;
+    bps = av_get_exact_bits_per_sample(avctx->codec_id);
+
+    /* codecs with an exact constant bits per sample */
+    if (bps > 0 && ch > 0 && frame_bytes > 0)
+        return (frame_bytes * 8) / (bps * ch);
+    bps = avctx->bits_per_coded_sample;
+
+    /* codecs with a fixed packet duration */
+    switch (id) {
+    case CODEC_ID_ADPCM_ADX:    return   32;
+    case CODEC_ID_ADPCM_IMA_QT: return   64;
+    case CODEC_ID_ADPCM_EA_XAS: return  128;
+    case CODEC_ID_AMR_NB:
+    case CODEC_ID_GSM:
+    case CODEC_ID_QCELP:
+    case CODEC_ID_RA_144:
+    case CODEC_ID_RA_288:       return  160;
+    case CODEC_ID_IMC:          return  256;
+    case CODEC_ID_AMR_WB:
+    case CODEC_ID_GSM_MS:       return  320;
+    case CODEC_ID_MP1:          return  384;
+    case CODEC_ID_ATRAC1:       return  512;
+    case CODEC_ID_ATRAC3:       return 1024;
+    case CODEC_ID_MP2:
+    case CODEC_ID_MUSEPACK7:    return 1152;
+    case CODEC_ID_AC3:          return 1536;
+    }
+
+    if (sr > 0) {
+        /* calc from sample rate */
+        if (id == CODEC_ID_TTA)
+            return 256 * sr / 245;
+
+        if (ch > 0) {
+            /* calc from sample rate and channels */
+            if (id == CODEC_ID_BINKAUDIO_DCT)
+                return (480 << (sr / 22050)) / ch;
+        }
+    }
+
+    if (ba > 0) {
+        /* calc from block_align */
+        if (id == CODEC_ID_SIPR) {
+            switch (ba) {
+            case 20: return 160;
+            case 19: return 144;
+            case 29: return 288;
+            case 37: return 480;
+            }
+        }
+    }
+
+    if (frame_bytes > 0) {
+        /* calc from frame_bytes only */
+        if (id == CODEC_ID_TRUESPEECH)
+            return 240 * (frame_bytes / 32);
+        if (id == CODEC_ID_NELLYMOSER)
+            return 256 * (frame_bytes / 64);
+
+        if (bps > 0) {
+            /* calc from frame_bytes and bits_per_coded_sample */
+            if (id == CODEC_ID_ADPCM_G726)
+                return frame_bytes * 8 / bps;
+        }
+
+        if (ch > 0) {
+            /* calc from frame_bytes and channels */
+            switch (id) {
+            case CODEC_ID_ADPCM_4XM:
+            case CODEC_ID_ADPCM_IMA_ISS:
+                return (frame_bytes - 4 * ch) * 2 / ch;
+            case CODEC_ID_ADPCM_IMA_SMJPEG:
+                return (frame_bytes - 4) * 2 / ch;
+            case CODEC_ID_ADPCM_IMA_AMV:
+                return (frame_bytes - 8) * 2 / ch;
+            case CODEC_ID_ADPCM_XA:
+                return (frame_bytes / 128) * 224 / ch;
+            case CODEC_ID_INTERPLAY_DPCM:
+                return (frame_bytes - 6 - ch) / ch;
+            case CODEC_ID_ROQ_DPCM:
+                return (frame_bytes - 8) / ch;
+            case CODEC_ID_XAN_DPCM:
+                return (frame_bytes - 2 * ch) / ch;
+            case CODEC_ID_MACE3:
+                return 3 * frame_bytes / ch;
+            case CODEC_ID_MACE6:
+                return 6 * frame_bytes / ch;
+            case CODEC_ID_PCM_LXF:
+                return 2 * (frame_bytes / (5 * ch));
+            }
+
+            if (tag) {
+                /* calc from frame_bytes, channels, and codec_tag */
+                if (id == CODEC_ID_SOL_DPCM) {
+                    if (tag == 3)
+                        return frame_bytes / ch;
+                    else
+                        return frame_bytes * 2 / ch;
+                }
+            }
+
+            if (ba > 0) {
+                /* calc from frame_bytes, channels, and block_align */
+                int blocks = frame_bytes / ba;
+                switch (avctx->codec_id) {
+                case CODEC_ID_ADPCM_IMA_WAV:
+                    return blocks * (1 + (ba - 4 * ch) / (4 * ch) * 8);
+                case CODEC_ID_ADPCM_IMA_DK3:
+                    return blocks * (((ba - 16) * 8 / 3) / ch);
+                case CODEC_ID_ADPCM_IMA_DK4:
+                    return blocks * (1 + (ba - 4 * ch) * 2 / ch);
+                case CODEC_ID_ADPCM_MS:
+                    return blocks * (2 + (ba - 7 * ch) * 2 / ch);
+                }
+            }
+
+            if (bps > 0) {
+                /* calc from frame_bytes, channels, and bits_per_coded_sample */
+                switch (avctx->codec_id) {
+                case CODEC_ID_PCM_DVD:
+                    return 2 * (frame_bytes / ((bps * 2 / 8) * ch));
+                case CODEC_ID_PCM_BLURAY:
+                    return frame_bytes / ((FFALIGN(ch, 2) * bps) / 8);
+                case CODEC_ID_S302M:
+                    return 2 * (frame_bytes / ((bps + 4) / 4)) / ch;
+                }
+            }
+        }
+    }
+
+    return 0;
+}
+
 #if !HAVE_THREADS
 int ff_thread_init(AVCodecContext *s){
     return -1;

libavcodec/version.h

@@ -21,7 +21,7 @@
 #define AVCODEC_VERSION_H
 
 #define LIBAVCODEC_VERSION_MAJOR 54
-#define LIBAVCODEC_VERSION_MINOR  7
+#define LIBAVCODEC_VERSION_MINOR  8
 #define LIBAVCODEC_VERSION_MICRO  0
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \