X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=libavutil%2Ftx.h;h=55173810ee9b99ab133214cf3b15e38722a82a85;hb=252500a78fe1a31abc79e6070d16f50382c39343;hp=53018c84e6b589b5d087dbd775cbd79b201f25c7;hpb=e8f054b095baa194623b3852f06fc507ae697503;p=ffmpeg

diff --git a/libavutil/tx.h b/libavutil/tx.h
index 53018c84e6b..55173810ee9 100644
--- a/libavutil/tx.h
+++ b/libavutil/tx.h
@@ -40,28 +40,46 @@ enum AVTXType {
     /**
      * Standard complex to complex FFT with sample data type AVComplexFloat.
      * Output is not 1/len normalized. Scaling currently unsupported.
+     * The stride parameter is ignored.
      */
     AV_TX_FLOAT_FFT = 0,
+
     /**
      * Standard MDCT with sample data type of float and a scale type of
      * float. Length is the frame size, not the window size (which is 2x frame)
+     * For forward transforms, the stride specifies the spacing between each
+     * sample in the output array in bytes. The input must be a flat array.
+     *
+     * For inverse transforms, the stride specifies the spacing between each
+     * sample in the input array in bytes. The output will be a flat array.
+     * Stride must be a non-zero multiple of sizeof(float).
+     *
+     * NOTE: the inverse transform is half-length, meaning the output will not
+     * contain redundant data. This is what most codecs work with. To do a full
+     * inverse transform, set the AV_TX_FULL_IMDCT flag on init.
      */
     AV_TX_FLOAT_MDCT = 1,
+
     /**
      * Same as AV_TX_FLOAT_FFT with a data type of AVComplexDouble.
      */
     AV_TX_DOUBLE_FFT = 2,
+
     /**
      * Same as AV_TX_FLOAT_MDCT with data and scale type of double.
+     * Stride must be a non-zero multiple of sizeof(double).
      */
     AV_TX_DOUBLE_MDCT = 3,
+
     /**
      * Same as AV_TX_FLOAT_FFT with a data type of AVComplexInt32.
      */
     AV_TX_INT32_FFT = 4,
+
     /**
      * Same as AV_TX_FLOAT_MDCT with data type of int32_t and scale type of float.
      * Only scale values less than or equal to 1.0 are supported.
+     * Stride must be a non-zero multiple of sizeof(int32_t).
      */
     AV_TX_INT32_MDCT = 5,
 };
@@ -75,15 +93,43 @@ enum AVTXType {
  * @param s the transform context
  * @param out the output array
  * @param in the input array
- * @param stride the input or output stride (depending on transform direction)
- * in bytes, currently implemented for all MDCT transforms
+ * @param stride the input or output stride in bytes
+ *
+ * The out and in arrays must be aligned to the maximum required by the CPU
+ * architecture unless the AV_TX_UNALIGNED flag was set in av_tx_init().
+ * The stride must follow the constraints the transform type has specified.
  */
 typedef void (*av_tx_fn)(AVTXContext *s, void *out, void *in, ptrdiff_t stride);
 
+/**
+ * Flags for av_tx_init()
+ */
+enum AVTXFlags {
+    /**
+     * Performs an in-place transformation on the input. The output argument
+     * of av_tn_fn() MUST match the input. May be unsupported or slower for some
+     * transform types.
+     */
+    AV_TX_INPLACE = 1ULL << 0,
+
+    /**
+     * Relaxes alignment requirement for the in and out arrays of av_tx_fn().
+     * May be slower with certain transform types.
+     */
+    AV_TX_UNALIGNED = 1ULL << 1,
+
+    /**
+     * Performs a full inverse MDCT rather than leaving out samples that can be
+     * derived through symmetry. Requires an output array of 'len' floats,
+     * rather than the usual 'len/2' floats.
+     * Ignored for all transforms but inverse MDCTs.
+     */
+    AV_TX_FULL_IMDCT = 1ULL << 2,
+};
+
 /**
  * Initialize a transform context with the given configuration
- * Currently power of two lengths from 4 to 131072 are supported, along with
- * any length decomposable to a power of two and either 3, 5 or 15.
+ * (i)MDCTs with an odd length are currently not supported.
  *
  * @param ctx the context to allocate, will be NULL on error
  * @param tx pointer to the transform function pointer to set
@@ -91,7 +137,7 @@ typedef void (*av_tx_fn)(AVTXContext *s, void *out, void *in, ptrdiff_t stride);
  * @param inv whether to do an inverse or a forward transform
  * @param len the size of the transform in samples
  * @param scale pointer to the value to scale the output if supported by type
- * @param flags currently unused
+ * @param flags a bitmask of AVTXFlags or 0
  *
  * @return 0 on success, negative error code on failure
  */