[FFmpeg-devel] [PATCH 5/5] avcodec/clearvideo: Avoid allocations when decoding tiles

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Up until now, the ClearVideo decoder separates parsing tiles
and actually using the parsed information: The information is
instead stored in structures which are constantly allocated
and freed. This commit changes this to use the information
immediately, avoiding said allocations. This e.g. reduced
the amount of allocations for [1] from 2,866,462 to 24,720.
For said sample decoding speed improved by 143%.

[1]: https://samples.ffmpeg.org/V-codecs/UCOD/AccordianDance-300.avi

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
 libavcodec/clearvideo.c | 99 +++++++++++++----------------------------
 1 file changed, 31 insertions(+), 68 deletions(-)

diff --git a/libavcodec/clearvideo.c b/libavcodec/clearvideo.c
index d3cbd71f72..e77661d187 100644
--- a/libavcodec/clearvideo.c
+++ b/libavcodec/clearvideo.c
@@ -59,13 +59,6 @@ typedef struct MVInfo {
     MV  *mv;
 } MVInfo;
 
-typedef struct TileInfo {
-    uint16_t        flags;
-    int16_t         bias;
-    MV              mv;
-    struct TileInfo *child[4];
-} TileInfo;
-
 typedef struct CLVContext {
     AVCodecContext *avctx;
     IDCTDSPContext idsp;
@@ -383,12 +376,16 @@ static int tile_do_block(AVCodecContext *avctx, AVFrame *dst, const AVFrame *src
     return ret;
 }
 
-static TileInfo *decode_tile_info(GetBitContext *gb, const LevelCodes *lc)
+static int decode_tile(AVCodecContext *avctx, GetBitContext *gb,
+                       const LevelCodes *lc,
+                       AVFrame *dst, const AVFrame *src,
+                       int plane, int x, int y, int size,
+                       MV root_mv, MV *pred)
 {
-    TileInfo *ti;
     int i, flags = 0;
     int16_t bias = 0;
     MV mv = { 0 };
+    int err;
 
     if (lc->flags_cb.table)
         flags = get_vlc2(gb, lc->flags_cb.table, CLV_VLC_BITS, 2);
@@ -403,7 +400,11 @@ static TileInfo *decode_tile_info(GetBitContext *gb, const LevelCodes *lc)
             mv.x = get_sbits(gb, 8);
             mv.y = get_sbits(gb, 8);
         }
+        if (pred)
+            mvi_update_prediction(pred, mv);
     }
+    mv.x += root_mv.x;
+    mv.y += root_mv.y;
 
     if (lc->bias_cb.table) {
         uint16_t bias_val = get_vlc2(gb, lc->bias_cb.table, CLV_VLC_BITS, 2);
@@ -415,55 +416,29 @@ static TileInfo *decode_tile_info(GetBitContext *gb, const LevelCodes *lc)
         }
     }
 
-    ti = av_calloc(1, sizeof(*ti));
-    if (!ti)
-        return NULL;
-
-    ti->flags = flags;
-    ti->mv = mv;
-    ti->bias = bias;
-
-    if (ti->flags) {
-        for (i = 0; i < 4; i++) {
-            if (ti->flags & (1 << i)) {
-                TileInfo *subti = decode_tile_info(gb, lc + 1);
-                ti->child[i] = subti;
-            }
-        }
-    }
-
-    return ti;
-}
-
-static int restore_tree(AVCodecContext *avctx, AVFrame *dst, AVFrame *src,
-                        int plane, int x, int y, int size,
-                        TileInfo *tile, MV root_mv)
-{
-    int ret;
-    MV mv;
-
-    mv.x = root_mv.x + tile->mv.x;
-    mv.y = root_mv.y + tile->mv.y;
-
-    if (!tile->flags) {
-        ret = tile_do_block(avctx, dst, src, plane, x, y, mv.x, mv.y, size, tile->bias);
-    } else {
-        int i, hsize = size >> 1;
-
+    if (flags) {
+        int hsize = size >> 1;
         for (i = 0; i < 4; i++) {
             int xoff = (i & 2) == 0 ? 0 : hsize;
             int yoff = (i & 1) == 0 ? 0 : hsize;
 
-            if (tile->child[i]) {
-                ret = restore_tree(avctx, dst, src, plane, x + xoff, y + yoff, hsize, tile->child[i], root_mv);
-                av_freep(&tile->child[i]);
+            if (flags & (1 << i)) {
+                err = decode_tile(avctx, gb, lc + 1, dst, src, plane,
+                                  x + xoff, y + yoff, hsize, root_mv, NULL);
             } else {
-                ret = tile_do_block(avctx, dst, src, plane, x + xoff, y + yoff, mv.x, mv.y, hsize, tile->bias);
+                err = tile_do_block(avctx, dst, src, plane, x + xoff, y + yoff,
+                                    mv.x, mv.y, hsize, bias);
             }
+            if (err < 0)
+                return err;
         }
+    } else {
+        err = tile_do_block(avctx, dst, src, plane, x, y, mv.x, mv.y, size, bias);
+        if (err < 0)
+            return err;
     }
 
-    return ret;
+    return 0;
 }
 
 static void extend_edges(AVFrame *buf, int tile_size)
@@ -604,38 +579,26 @@ static int clv_decode_frame(AVCodecContext *avctx, AVFrame *rframe,
                     int x = i << c->tile_shift;
                     int y = j << c->tile_shift;
                     int size = 1 << c->tile_shift;
-                    TileInfo *tile;
                     MV cmv;
 
-                    tile = decode_tile_info(&c->gb, &lev[0]); // Y
-                    if (!tile)
-                        return AVERROR(ENOMEM);
-                    ret = restore_tree(avctx, c->pic, c->prev, 0, x, y, size, tile, mv);
+                    ret = decode_tile(avctx, &c->gb, &lev[0], c->pic, c->prev,  // Y
+                                      0, x, y, size, mv, mvp);
                     if (ret < 0)
                         mb_ret = ret;
-                    mvi_update_prediction(mvp, tile->mv);
                     x = i << (c->tile_shift - 1);
                     y = j << (c->tile_shift - 1);
                     size = 1 << (c->tile_shift - 1);
-                    cmv.x = mv.x + tile->mv.x;
-                    cmv.y = mv.y + tile->mv.y;
+                    cmv = *mvp;
                     cmv.x /= 2;
                     cmv.y /= 2;
-                    av_freep(&tile);
-                    tile = decode_tile_info(&c->gb, &lev[4]); // U
-                    if (!tile)
-                        return AVERROR(ENOMEM);
-                    ret = restore_tree(avctx, c->pic, c->prev, 1, x, y, size, tile, cmv);
+                    ret = decode_tile(avctx, &c->gb, &lev[4], c->pic, c->prev,  // U
+                                      1, x, y, size, cmv, NULL);
                     if (ret < 0)
                         mb_ret = ret;
-                    av_freep(&tile);
-                    tile = decode_tile_info(&c->gb, &lev[7]); // V
-                    if (!tile)
-                        return AVERROR(ENOMEM);
-                    ret = restore_tree(avctx, c->pic, c->prev, 2, x, y, size, tile, cmv);
+                    ret = decode_tile(avctx, &c->gb, &lev[7], c->pic, c->prev,  // U
+                                      2, x, y, size, cmv, NULL);
                     if (ret < 0)
                         mb_ret = ret;
-                    av_freep(&tile);
                 }
             }
             mvi_update_row(&c->mvi);
-- 
2.34.1

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