Fixes multistream doc
diff --git a/include/opus_multistream.h b/include/opus_multistream.h
index be1b44d..f476efa 100644
--- a/include/opus_multistream.h
+++ b/include/opus_multistream.h
@@ -68,7 +68,7 @@
* well.
* In addition, you may retrieve the encoder or decoder state for an specific
* stream via #OPUS_MULTISTREAM_GET_ENCODER_STATE or
- * #OPUS_MULTISTREAM_GET_DECODER and apply CTLs to it individually.
+ * #OPUS_MULTISTREAM_GET_DECODER_STATE and apply CTLs to it individually.
*/
/**@{*/
@@ -111,8 +111,9 @@
* duration, can be computed without any special negotation.
*
* The format for multistream Opus packets is defined in the
- * <a href="http://tools.ietf.org/html/draft-terriberry-oggopus-01">Ogg
- * encapsulation specification</a>.
+ * <a href="http://tools.ietf.org/html/draft-terriberry-oggopus">Ogg
+ * encapsulation specification</a> and is based on the self-delimited Opus
+ * framing described in Appendix B of <a href="http://tools.ietf.org/html/rfc6716">RFC 6716</a>.
* Normal Opus packets are just a degenerate case of multistream Opus packets,
* and can be encoded or decoded with the multistream API by setting
* <code>streams</code> to <code>1</code> when initializing the encoder or
@@ -124,13 +125,25 @@
* The streams are ordered so that all coupled streams appear at the
* beginning.
*
- * A <code>mapping</code> table defines which decoded channel should be used
- * for each output channel. The output channels specified by the encoder
+ * A <code>mapping</code> table defines which decoded channel <code>i</code>
+ * should be used for each input/output (I/O) channel <code>j</code>. This table is
+ * typically provided as an unsigned char array.
+ * Let <code>i = mapping[j]</code> be the index for I/O channel <code>j</code>.
+ * If <code>i < 2*coupled_streams</code>, then I/O channel <code>j</code> is
+ * encoded as the left channel of stream <code>(i/2)</code> if <code>i</code>
+ * is even, or as the right channel of stream <code>(i/2)</code> if
+ * <code>i</code> is odd. Otherwise, I/O channel <code>j</code> is encoded as
+ * mono in stream <code>(i - coupled_streams)</code>, unless it has the special
+ * value 255, in which case it is omitted from the encoding entirely (the
+ * decoder will reproduce it as silence). Each value <code>i</code> must either
+ * be the special value 255 or be less than <code>streams + coupled_streams</code>.
+ *
+ * The output channels specified by the encoder
* should use the
* <a href="http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-800004.3.9">Vorbis
* channel ordering</a>. A decoder may wish to apply an additional permutation
* to the mapping the encoder used to achieve a different output channel
- * order.
+ * order (e.g. for outputing in WAV order).
*
* Each multistream packet contains an Opus packet for each stream, and all of
* the Opus packets in a single multistream packet must have the same
@@ -200,12 +213,12 @@
* 24000, or 48000.
* @param channels <tt>int</tt>: Number of channels in the input signal.
* This must be at most 255.
- * It may be different from the number of
- * channels (<code>streams +
+ * It may be greater than the number of
+ * coded channels (<code>streams +
* coupled_streams</code>).
* @param streams <tt>int</tt>: The total number of streams to encode from the
* input.
- * This must be no more than 255.
+ * This must be no more than the number of channels.
* @param coupled_streams <tt>int</tt>: Number of coupled (2 channel) streams
* to encode.
* This must be no larger than the total
@@ -213,24 +226,13 @@
* Additionally, The total number of
* encoded channels (<code>streams +
* coupled_streams</code>) must be no
- * more than 255.
+ * more than the number of input channels.
* @param[in] mapping <code>const unsigned char[channels]</code>: Mapping from
- * encoded channels to input channels.
- * Let <code>i = mapping[j]</code> be the index for input
- * channel <code>j</code>.
- * If <code>i < 2*coupled_streams</code>, then input
- * channel <code>j</code> is encoded as the left channel of
- * stream <code>(i/2)</code> if <code>i</code> is even, and
- * as the right channel of stream <code>(i/2)</code> if
- * <code>i</code> is odd.
- * Otherwise, input channel <code>j</code> is encoded as
- * mono in stream <code>(i - coupled_streams)</code>,
- * unless it has the special value 255, in which case it is
- * omitted from the encoding entirely (the decoder will
- * reproduce it as silence).
- * Each value <code>i</code> must either be the special
- * value 255 or be less than
- * <code>streams + coupled_streams</code>.
+ * encoded channels to input channels, as described in
+ * @ref opus_multistream. As an extra constraint, the
+ * multistream encoder does not allow encoding coupled
+ * streams for which one channel is unused since this
+ * is never a good idea.
* @param application <tt>int</tt>: The target encoder application.
* This must be one of the following:
* <dl>
@@ -257,7 +259,7 @@
) OPUS_ARG_NONNULL(5);
/** Initialize a previously allocated multistream encoder state.
- * The memory pointed to by \a st must be the size returned by
+ * The memory pointed to by \a st must be at least the size returned by
* opus_multistream_encoder_get_size().
* This is intended for applications which use their own allocator instead of
* malloc.
@@ -270,12 +272,12 @@
* 24000, or 48000.
* @param channels <tt>int</tt>: Number of channels in the input signal.
* This must be at most 255.
- * It may be different from the number of
+ * It may be greater than the number of
* coded channels (<code>streams +
* coupled_streams</code>).
* @param streams <tt>int</tt>: The total number of streams to encode from the
* input.
- * This must be no more than 255.
+ * This must be no more than the number of channels.
* @param coupled_streams <tt>int</tt>: Number of coupled (2 channel) streams
* to encode.
* This must be no larger than the total
@@ -283,10 +285,13 @@
* Additionally, The total number of
* encoded channels (<code>streams +
* coupled_streams</code>) must be no
- * more than 255.
+ * more than the number of input channels.
* @param[in] mapping <code>const unsigned char[channels]</code>: Mapping from
- * encoded channels to input channels.
- * See opus_multistream_encoder_create() for details.
+ * encoded channels to input channels, as described in
+ * @ref opus_multistream. As an extra constraint, the
+ * multistream encoder does not allow encoding coupled
+ * streams for which one channel is unused since this
+ * is never a good idea.
* @param application <tt>int</tt>: The target encoder application.
* This must be one of the following:
* <dl>
@@ -314,7 +319,7 @@
/** Encodes a multistream Opus frame.
* @param st <tt>OpusMSEncoder*</tt>: Multistream encoder state.
* @param[in] pcm <tt>const opus_int16*</tt>: The input signal as interleaved
- * samples.
+ * samples.
* This must contain
* <code>frame_size*channels</code>
* samples.
@@ -331,9 +336,11 @@
* This must contain storage for at
* least \a max_data_bytes.
* @param max_data_bytes <tt>opus_int32</tt>: Size of the allocated memory for
- * the output payload.
- * This should not be used by
- * itself to control the bitrate.
+ * the output payload. This may be
+ * used to impose an upper limit on
+ * the variable bitrate, but should
+ * not be used as the only bitrate
+ * control.
* @returns The length of the encoded packet (in bytes) on success or a
* negative error code (see @ref opus_errorcodes) on failure.
*/
@@ -372,9 +379,11 @@
* This must contain storage for at
* least \a max_data_bytes.
* @param max_data_bytes <tt>opus_int32</tt>: Size of the allocated memory for
- * the output payload.
- * This should not be used by
- * itself to control the bitrate.
+ * the output payload. This may be
+ * used to impose an upper limit on
+ * the variable bitrate, but should
+ * not be used as the only bitrate
+ * control.
* @returns The length of the encoded packet (in bytes) on success or a
* negative error code (see @ref opus_errorcodes) on failure.
*/
@@ -437,7 +446,7 @@
* @param Fs <tt>opus_int32</tt>: Sampling rate to decode at (in Hz).
* This must be one of 8000, 12000, 16000,
* 24000, or 48000.
- * @param channels <tt>int</tt>: Number of channels to decode.
+ * @param channels <tt>int</tt>: Number of channels to output.
* This must be at most 255.
* It may be different from the number of coded
* channels (<code>streams +
@@ -454,21 +463,8 @@
* coupled_streams</code>) must be no
* more than 255.
* @param[in] mapping <code>const unsigned char[channels]</code>: Mapping from
- * coded channels to output channels.
- * Let <code>i = mapping[j]</code> be the index for output
- * channel <code>j</code>.
- * If <code>i < 2*coupled_streams</code>, then the output
- * for channel <code>j</code> is taken from the left
- * channel of stream <code>(i/2)</code> if <code>i</code>
- * <code>i</code> is even, and from the right channel of
- * stream <code>(i/2)</code> if <code>i</code> is odd.
- * Otherwise, the output for channel <code>j</code> is
- * taken from stream <code>(i - coupled_streams)</code>
- * decoded as mono, unless it has the special value 255, in
- * which case silence is used instead.
- * Each value <code>i</code> must either be the special
- * value 255 or be less than
- * <code>streams + coupled_streams</code>.
+ * coded channels to output channels, as described in
+ * @ref opus_multistream.
* @param[out] error <tt>int *</tt>: Returns #OPUS_OK on success, or an error
* code (see @ref opus_errorcodes) on
* failure.
@@ -483,7 +479,7 @@
) OPUS_ARG_NONNULL(5);
/** Intialize a previously allocated decoder state object.
- * The memory pointed to by \a st must be the size returned by
+ * The memory pointed to by \a st must be at least the size returned by
* opus_multistream_encoder_get_size().
* This is intended for applications which use their own allocator instead of
* malloc.
@@ -494,7 +490,7 @@
* @param Fs <tt>opus_int32</tt>: Sampling rate to decode at (in Hz).
* This must be one of 8000, 12000, 16000,
* 24000, or 48000.
- * @param channels <tt>int</tt>: Number of channels to decode.
+ * @param channels <tt>int</tt>: Number of channels to output.
* This must be at most 255.
* It may be different from the number of coded
* channels (<code>streams +
@@ -511,8 +507,8 @@
* coupled_streams</code>) must be no
* more than 255.
* @param[in] mapping <code>const unsigned char[channels]</code>: Mapping from
- * coded channels to output channels.
- * See opus_multistream_decoder_create() for details.
+ * coded channels to output channels, as described in
+ * @ref opus_multistream.
* @returns #OPUS_OK on success, or an error code (see @ref opus_errorcodes)
* on failure.
*/