1 files changed, 23 insertions, 8 deletions
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 2b7ac65c13..69e541a8f0 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -745,10 +745,22 @@ typedef struct RcOverride{
 /* Codec can export data for HW decoding (XvMC). */
 #define CODEC_CAP_HWACCEL         0x0010
 /**
- * Codec has a nonzero delay and needs to be fed with avpkt->data=NULL,
+ * Encoder or decoder requires flushing with NULL input at the end in order to
+ * give the complete and correct output.
+ *
+ * NOTE: If this flag is not set, the codec is guaranteed to never be fed with
+ *       with NULL data. The user can still send NULL data to the public encode
+ *       or decode function, but libavcodec will not pass it along to the codec
+ *       unless this flag is set.
+ *
+ * Decoders:
+ * The decoder has a non-zero delay and needs to be fed with avpkt->data=NULL,
  * avpkt->size=0 at the end to get the delayed data until the decoder no longer
- * returns frames. If this is not set, the codec is guaranteed to never be fed
- * with NULL data.
+ * returns frames.
+ *
+ * Encoders:
+ * The encoder needs to be fed with NULL data at the end of encoding until the
+ * encoder no longer returns data.
  */
 #define CODEC_CAP_DELAY           0x0020
 /**
@@ -4318,9 +4330,9 @@ void avsubtitle_free(AVSubtitle *sub);
  * Encode an audio frame from samples into buf.
  *
  * @note The output buffer should be at least FF_MIN_BUFFER_SIZE bytes large.
- * However, for PCM audio the user will know how much space is needed
- * because it depends on the value passed in buf_size as described
- * below. In that case a lower value can be used.
+ * However, for codecs with avctx->frame_size equal to 0 (e.g. PCM) the user
+ * will know how much space is needed because it depends on the value passed
+ * in buf_size as described below. In that case a lower value can be used.
  *
  * @param avctx the codec context
  * @param[out] buf the output buffer
@@ -4328,8 +4340,11 @@ void avsubtitle_free(AVSubtitle *sub);
  * @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 avctx.
- * For PCM audio the number of samples read from samples is equal to
- * buf_size * input_sample_size / output_sample_size.
+ * For codecs which have avctx->frame_size equal to 0 (e.g. PCM) the number of
+ * samples read from samples is equal to:
+ * buf_size * 8 / (avctx->channels * av_get_bits_per_sample(avctx->codec_id))
+ * This also implies that av_get_bits_per_sample() must not return 0 for these
+ * codecs.
  * @return On error a negative value is returned, on success zero or the number
  * of bytes used to encode the data read from the input buffer.
  */