av_get_audio_frame_duration: add ADPCM_AFC

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/utils.c

@@ -2465,6 +2465,8 @@ int av_get_audio_frame_duration(AVCodecContext *avctx, int frame_bytes)
         if (ch > 0) {
             /* calc from frame_bytes and channels */
             switch (id) {
+            case AV_CODEC_ID_ADPCM_AFC:
+                return frame_bytes / (9 * ch) * 16;
             case AV_CODEC_ID_ADPCM_4XM:
             case AV_CODEC_ID_ADPCM_IMA_ISS:
                 return (frame_bytes - 4 * ch) * 2 / ch;