Clarify documentation for avcodec_encode_audio.

patch by Stefano Sabatini, stefano.sabatini-lala poste it

Originally committed as revision 11108 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/avcodec.h

@@ -2674,8 +2674,10 @@ int avcodec_parse_frame(AVCodecContext *avctx, uint8_t **pdata,
  * @param[out] buf the output buffer
  * @param[in] buf_size the output buffer size
  * @param[in] samples the input buffer containing the samples
+ * The number of samples read from this buffer is frame_size*channels,
+ * both of which are defined in \p avctx.
  * @return On error a negative value is returned, on succes zero or the number
- * of bytes used from the input buffer.
+ * of bytes used to encode the data read from the input buffer.
  */
 int avcodec_encode_audio(AVCodecContext *avctx, uint8_t *buf, int buf_size,
                          const short *samples);