[FFmpeg-devel] [PATCH] lavc/dxv: align to 4x4 blocks instead of 16x16

[Connor Worley]

The previous assumption that DXV needs to be aligned to 16x16 was
erroneous. 4x4 works just as well, and FATE decoder tests pass for all
texture formats.

On the encoder side, we should reject input that isn't 4x4 aligned,
like the HAP encoder does, and stop aligning to 16x16. This both solves
the uninitialized reads causing current FATE tests to fail and produces
smaller encoded outputs.

Signed-off-by: Connor Worley <connorbworley at gmail.com>
---
 libavcodec/dxv.c            |  6 +++---
 libavcodec/dxvenc.c         | 13 ++++++++++---
 tests/ref/fate/dxv3enc-dxt1 |  2 +-
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/libavcodec/dxv.c b/libavcodec/dxv.c
index e1c7cee3e8..9261a5cac1 100644
--- a/libavcodec/dxv.c
+++ b/libavcodec/dxv.c
@@ -1238,9 +1238,9 @@ static int dxv_init(AVCodecContext *avctx)
         return ret;
     }
 
-    /* Codec requires 16x16 alignment. */
-    avctx->coded_width  = FFALIGN(avctx->width,  16);
-    avctx->coded_height = FFALIGN(avctx->height, 16);
+    /* Since codec is based on 4x4 blocks, size is aligned to 4 */
+    avctx->coded_width  = FFALIGN(avctx->width,  TEXTURE_BLOCK_W);
+    avctx->coded_height = FFALIGN(avctx->height, TEXTURE_BLOCK_H);
 
     ff_texturedsp_init(&ctx->texdsp);
 
diff --git a/libavcodec/dxvenc.c b/libavcodec/dxvenc.c
index ebc48aace3..3023a6da6c 100644
--- a/libavcodec/dxvenc.c
+++ b/libavcodec/dxvenc.c
@@ -216,6 +216,13 @@ static av_cold int dxv_init(AVCodecContext *avctx)
         return ret;
     }
 
+    if (avctx->width % TEXTURE_BLOCK_W || avctx->height % TEXTURE_BLOCK_H) {
+        av_log(avctx, AV_LOG_ERROR, "Video size %dx%d is not multiple of %dx%d.\n",
+               avctx->width, avctx->height,
+               TEXTURE_BLOCK_W, TEXTURE_BLOCK_H);
+        return AVERROR_INVALIDDATA;
+    }
+
     ff_texturedspenc_init(&texdsp);
 
     switch (ctx->tex_fmt) {
@@ -229,10 +236,10 @@ static av_cold int dxv_init(AVCodecContext *avctx)
         return AVERROR_INVALIDDATA;
     }
     ctx->enc.raw_ratio = 16;
-    ctx->tex_size = FFALIGN(avctx->width, 16) / TEXTURE_BLOCK_W *
-                    FFALIGN(avctx->height, 16) / TEXTURE_BLOCK_H *
+    ctx->tex_size = avctx->width  / TEXTURE_BLOCK_W *
+                    avctx->height / TEXTURE_BLOCK_H *
                     ctx->enc.tex_ratio;
-    ctx->enc.slice_count = av_clip(avctx->thread_count, 1, FFALIGN(avctx->height, 16) / TEXTURE_BLOCK_H);
+    ctx->enc.slice_count = av_clip(avctx->thread_count, 1, avctx->height / TEXTURE_BLOCK_H);
 
     ctx->tex_data = av_malloc(ctx->tex_size);
     if (!ctx->tex_data) {
diff --git a/tests/ref/fate/dxv3enc-dxt1 b/tests/ref/fate/dxv3enc-dxt1
index 3cfd73397e..74849a8031 100644
--- a/tests/ref/fate/dxv3enc-dxt1
+++ b/tests/ref/fate/dxv3enc-dxt1
@@ -3,4 +3,4 @@
 #codec_id 0: dxv
 #dimensions 0: 1920x1080
 #sar 0: 1/1
-0,          0,          0,        1,    76767, 0x932ecbfa
+0,          0,          0,        1,    76521, 0xed387a5e
-- 
2.40.1