diff --git a/va/va.h b/va/va.h
index 127ad49..01694a9 100644
--- a/va/va.h
+++ b/va/va.h
@@ -1185,13 +1185,21 @@
 /** MPEG-2 Inverse Quantization Matrix Buffer */
 typedef struct _VAIQMatrixBufferMPEG2
 {
+    /** \brief Same as the MPEG-2 bitstream syntax element. */
     int load_intra_quantiser_matrix;
+    /** \brief Same as the MPEG-2 bitstream syntax element. */
     int load_non_intra_quantiser_matrix;
+    /** \brief Same as the MPEG-2 bitstream syntax element. */
     int load_chroma_intra_quantiser_matrix;
+    /** \brief Same as the MPEG-2 bitstream syntax element. */
     int load_chroma_non_intra_quantiser_matrix;
+    /** \brief Luminance intra matrix, in zig-zag scan order. */
     unsigned char intra_quantiser_matrix[64];
+    /** \brief Luminance non-intra matrix, in zig-zag scan order. */
     unsigned char non_intra_quantiser_matrix[64];
+    /** \brief Chroma intra matrix, in zig-zag scan order. */
     unsigned char chroma_intra_quantiser_matrix[64];
+    /** \brief Chroma non-intra matrix, in zig-zag scan order. */
     unsigned char chroma_non_intra_quantiser_matrix[64];
 } VAIQMatrixBufferMPEG2;
 
@@ -1321,9 +1329,13 @@
 /** MPEG-4 Inverse Quantization Matrix Buffer */
 typedef struct _VAIQMatrixBufferMPEG4
 {
+    /** Same as the MPEG-4:2 bitstream syntax element. */
     int load_intra_quant_mat;
+    /** Same as the MPEG-4:2 bitstream syntax element. */
     int load_non_intra_quant_mat;
+    /** The matrix for intra blocks, in zig-zag scan order. */
     unsigned char intra_quant_mat[64];
+    /** The matrix for non-intra blocks, in zig-zag scan order. */
     unsigned char non_intra_quant_mat[64];
 } VAIQMatrixBufferMPEG4;
 
@@ -1620,7 +1632,9 @@
 /** H.264 Inverse Quantization Matrix Buffer */
 typedef struct _VAIQMatrixBufferH264
 {
+    /** \brief 4x4 scaling list, in raster scan order. */
     unsigned char ScalingList4x4[6][16];
+    /** \brief 8x8 scaling list, in raster scan order. */
     unsigned char ScalingList8x8[2][64];
 } VAIQMatrixBufferH264;
 
diff --git a/va/va_dec_jpeg.h b/va/va_dec_jpeg.h
index 9936692..380e0fe 100644
--- a/va/va_dec_jpeg.h
+++ b/va/va_dec_jpeg.h
@@ -83,6 +83,8 @@
  * The #load_quantization_table array can be used as a hint to notify
  * the VA driver implementation about which table(s) actually changed
  * since the last submission of this buffer.
+ *
+ * The #quantiser_table values are specified in zig-zag scan order.
  */
 typedef struct _VAIQMatrixBufferJPEGBaseline {
     /** \brief Specifies which #quantiser_table is valid. */