[FFmpeg-devel] [PATCH 3/3] avutil/frame: also align data pointers in av_frame_get_buffer()

[James Almer]

From: Pavel Koshevoy <pkoshevoy at gmail.com>

This avoids unpleasant surprises to av_frame_get_buffer callers
that explicitly specified 64-byte alignment and didn't get
AVFrame.data pointers that are 64-byte aligned.

For example, see https://github.com/sekrit-twc/zimg/issues/212

Although the zscale issue has already been resolved by other means
it would still be prudent to improve the behavior of av_frame_get_buffer
to fix any unknown and future instances of similar issues.

Co-authored-by: James Almer <jamrial at gmail.com>
Signed-off-by: James Almer <jamrial at gmail.com>
---
 doc/APIchanges      |  4 ++++
 libavutil/frame.c   | 21 ++++++++++++++++-----
 libavutil/frame.h   |  7 ++++---
 libavutil/version.h |  2 +-
 4 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/doc/APIchanges b/doc/APIchanges
index 15606cafac..d477904856 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -2,6 +2,10 @@ The last version increases of all libraries were on 2024-03-07
 
 API changes, most recent first:
 
+2024-11-16 - xxxxxxxxxx - lavu 59.47.101 - frame.h
+  av_frame_get_buffer() now also aligns the data pointers according to
+  the requested alignment.
+
 2024-11-13 - xxxxxxxxxx - lavu 59.47.100 - channel_layout.h
   Add AV_CHAN_BINAURAL_LEFT, AV_CHAN_BINAURAL_RIGHT
   Add AV_CH_BINAURAL_LEFT, AV_CH_BINAURAL_RIGHT
diff --git a/libavutil/frame.c b/libavutil/frame.c
index 093853b173..5fb47dbaa6 100644
--- a/libavutil/frame.c
+++ b/libavutil/frame.c
@@ -210,7 +210,7 @@ static int get_video_buffer(AVFrame *frame, int align)
                                          padded_height, linesizes)) < 0)
         return ret;
 
-    total_size = 4*plane_padding;
+    total_size = 4 * plane_padding + 4 * align;
     for (int i = 0; i < 4; i++) {
         if (sizes[i] > SIZE_MAX - total_size)
             return AVERROR(EINVAL);
@@ -230,6 +230,7 @@ static int get_video_buffer(AVFrame *frame, int align)
     for (int i = 1; i < 4; i++) {
         if (frame->data[i])
             frame->data[i] += i * plane_padding;
+        frame->data[i] = (uint8_t *)FFALIGN((uintptr_t)frame->data[i], align);
     }
 
     frame->extended_data = frame->data;
@@ -244,6 +245,7 @@ static int get_audio_buffer(AVFrame *frame, int align)
 {
     int planar   = av_sample_fmt_is_planar(frame->format);
     int channels, planes;
+    size_t size;
     int ret;
 
     channels = frame->ch_layout.nb_channels;
@@ -256,6 +258,9 @@ static int get_audio_buffer(AVFrame *frame, int align)
             return ret;
     }
 
+    if (align <= 0)
+        align = ALIGN;
+
     if (planes > AV_NUM_DATA_POINTERS) {
         frame->extended_data = av_calloc(planes,
                                           sizeof(*frame->extended_data));
@@ -270,21 +275,27 @@ static int get_audio_buffer(AVFrame *frame, int align)
     } else
         frame->extended_data = frame->data;
 
+    if (frame->linesize[0] > SIZE_MAX - align)
+        return AVERROR(EINVAL);
+    size = frame->linesize[0] + (size_t)align;
+
     for (int i = 0; i < FFMIN(planes, AV_NUM_DATA_POINTERS); i++) {
-        frame->buf[i] = av_buffer_alloc(frame->linesize[0]);
+        frame->buf[i] = av_buffer_alloc(size);
         if (!frame->buf[i]) {
             av_frame_unref(frame);
             return AVERROR(ENOMEM);
         }
-        frame->extended_data[i] = frame->data[i] = frame->buf[i]->data;
+        frame->extended_data[i] = frame->data[i] =
+            (uint8_t *)FFALIGN((uintptr_t)frame->buf[i]->data, align);
     }
     for (int i = 0; i < planes - AV_NUM_DATA_POINTERS; i++) {
-        frame->extended_buf[i] = av_buffer_alloc(frame->linesize[0]);
+        frame->extended_buf[i] = av_buffer_alloc(size);
         if (!frame->extended_buf[i]) {
             av_frame_unref(frame);
             return AVERROR(ENOMEM);
         }
-        frame->extended_data[i + AV_NUM_DATA_POINTERS] = frame->extended_buf[i]->data;
+        frame->extended_data[i + AV_NUM_DATA_POINTERS] =
+            (uint8_t *)FFALIGN((uintptr_t)frame->extended_buf[i]->data, align);
     }
     return 0;
 
diff --git a/libavutil/frame.h b/libavutil/frame.h
index f7806566d5..c107f43bc0 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -887,9 +887,10 @@ void av_frame_move_ref(AVFrame *dst, AVFrame *src);
  *           cases.
  *
  * @param frame frame in which to store the new buffers.
- * @param align Required buffer size alignment. If equal to 0, alignment will be
- *              chosen automatically for the current CPU. It is highly
- *              recommended to pass 0 here unless you know what you are doing.
+ * @param align Required buffer size and data pointer alignment. If equal to 0,
+ *              alignment will be chosen automatically for the current CPU.
+ *              It is highly recommended to pass 0 here unless you know what
+ *              you are doing.
  *
  * @return 0 on success, a negative AVERROR on error.
  */
diff --git a/libavutil/version.h b/libavutil/version.h
index c1878a49ad..6a4abcf7f5 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -80,7 +80,7 @@
 
 #define LIBAVUTIL_VERSION_MAJOR  59
 #define LIBAVUTIL_VERSION_MINOR  47
-#define LIBAVUTIL_VERSION_MICRO 100
+#define LIBAVUTIL_VERSION_MICRO 101
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
                                                LIBAVUTIL_VERSION_MINOR, \
-- 
2.47.0