avcodec/utils: Introduce avcodec_align_dimensions3, which returns a…

… single linesize alignment value

`avcodec_align_dimensions2` returns an array of linesize alignment values even though all the values are the same. This API is less friendly to a custom `AVFrame` buffer allocator because some non-FFmpeg image libraries only accept a single linesize alignment value for all the planes (e.g. Core Video). Therefore, introduce `avcodec_align_dimensions3`, which returns a single linesize alignment value.

libavcodec/avcodec.h

@@ -2348,7 +2348,7 @@ typedef struct AVCodecContext {
      * If AV_GET_BUFFER_FLAG_REF is set in flags then the frame may be reused
      * (read and/or written to if it is writable) later by libavcodec.
      *
-     * avcodec_align_dimensions2() should be used to find the required width and
+     * avcodec_align_dimensions3() should be used to find the required width and
      * height, as they normally need to be rounded up to the next multiple of 16.
      *
      * Some decoders do not support linesizes changing between frames.
@@ -2357,7 +2357,7 @@ typedef struct AVCodecContext {
      * this callback may be called from a different thread, but not from more
      * than one at once. Does not need to be reentrant.
      *
-     * @see avcodec_align_dimensions2()
+     * @see avcodec_align_dimensions3()
      *
      * Audio:
      *
@@ -4685,21 +4685,25 @@ int avcodec_default_get_buffer2(AVCodecContext *s, AVFrame *frame, int flags);
  * Modify width and height values so that they will result in a memory
  * buffer that is acceptable for the codec if you do not use any horizontal
  * padding.
- *
- * May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
  */
 void avcodec_align_dimensions(AVCodecContext *s, int *width, int *height);
 
 /**
  * Modify width and height values so that they will result in a memory
  * buffer that is acceptable for the codec if you also ensure that all
  * line sizes are a multiple of the respective linesize_align[i].
- *
- * May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
  */
 void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
                                int linesize_align[AV_NUM_DATA_POINTERS]);
 
+/**
+ * Modify width and height values so that they will result in a memory
+ * buffer that is acceptable for the codec if you also ensure that all
+ * line sizes are a multiple of linesize_align.
+ */
+void avcodec_align_dimensions3(AVCodecContext *s, int *width, int *height,
+                               int *linesize_align);
+
 /**
  * Converts AVChromaLocation to swscale x/y chroma position.
  *

libavcodec/decode.c

@@ -1542,7 +1542,7 @@ static int update_frame_pool(AVCodecContext *avctx, AVFrame *frame)
             pool->width == frame->width && pool->height == frame->height)
             return 0;
 
-        avcodec_align_dimensions2(avctx, &w, &h, pool->stride_align);
+        avcodec_align_dimensions3(avctx, &w, &h, &pool->stride_align);
 
         do {
             // NOTE: do not align linesizes individually, this breaks e.g. assumptions
@@ -1555,7 +1555,7 @@ static int update_frame_pool(AVCodecContext *avctx, AVFrame *frame)
 
             unaligned = 0;
             for (i = 0; i < 4; i++)
-                unaligned |= linesize[i] % pool->stride_align[i];
+                unaligned |= linesize[i] % pool->stride_align;
         } while (unaligned);
 
         tmpsize = av_image_fill_pointers(data, avctx->pix_fmt, h,

libavcodec/internal.h

@@ -109,7 +109,7 @@ typedef struct FramePool {
      */
     int format;
     int width, height;
-    int stride_align[AV_NUM_DATA_POINTERS];
+    int stride_align;
     int linesize[4];
     int planes;
     int channels;

libavcodec/utils.c

@@ -151,10 +151,9 @@ int ff_side_data_update_matrix_encoding(AVFrame *frame,
     return 0;
 }
 
-void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
-                               int linesize_align[AV_NUM_DATA_POINTERS])
+void avcodec_align_dimensions3(AVCodecContext *s, int *width, int *height,
+                               int *linesize_align)
 {
-    int i;
     int w_align = 1;
     int h_align = 1;
     AVPixFmtDescriptor const *desc = av_pix_fmt_desc_get(s->pix_fmt);
@@ -331,8 +330,18 @@ void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
         *width = FFMAX(*width, 32);
     }
 
-    for (i = 0; i < 4; i++)
-        linesize_align[i] = STRIDE_ALIGN;
+    *linesize_align = STRIDE_ALIGN;
+}
+
+void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
+                               int linesize_align[AV_NUM_DATA_POINTERS])
+{
+    int i;
+
+    avcodec_align_dimensions3(s, width, height, linesize_align);
+
+    for (i = 1; i < 4; i++)
+        linesize_align[i] = linesize_align[0];
 }
 
 void avcodec_align_dimensions(AVCodecContext *s, int *width, int *height)

libavutil/frame.h

@@ -299,7 +299,7 @@ typedef struct AVFrame {
      * This might be different from the first allocated byte
      *
      * Some decoders access areas outside 0,0 - width,height, please
-     * see avcodec_align_dimensions2(). Some filters and swscale can read
+     * see avcodec_align_dimensions3(). Some filters and swscale can read
      * up to 16 bytes beyond the planes, if these filters are to be used,
      * then 16 extra bytes must be allocated.
      *