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lavc/dxvenc: migrate DXT1 encoder to lavc hashtable

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Offers a modest performance gain due to the switch from naive linear
probling to robin hood.

Signed-off-by: Emma Worley <emma@emma.gg>
This commit is contained in:
Emma Worley
2025-05-30 16:20:07 -07:00
parent 6fdb54ddee
commit 2de0d095b8
2 changed files with 35 additions and 90 deletions
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2
libavcodec/dxv.h
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@ -1,6 +1,6 @@
/*
* Resolume DXV common
* Copyright (C) 2024 Connor Worley <connorbworley@gmail.com>
* Copyright (C) 2024 Emma Worley <emma@emma.gg>
*
* This file is part of FFmpeg.
*

123
libavcodec/dxvenc.c
View File

@ -1,6 +1,6 @@
/*
* Resolume DXV encoder
* Copyright (C) 2024 Connor Worley <connorbworley@gmail.com>
* Copyright (C) 2024 Emma Worley <emma@emma.gg>
*
* This file is part of FFmpeg.
*
@ -21,7 +21,7 @@
#include <stdint.h>
#include "libavutil/crc.h"
#include "libavcodec/hashtable.h"
#include "libavutil/imgutils.h"
#include "libavutil/mem.h"
#include "libavutil/opt.h"
@ -39,72 +39,9 @@
* appeared in the decompressed stream. Using a simple hash table (HT)
* significantly speeds up the lookback process while encoding.
*/
#define LOOKBACK_HT_ELEMS 0x40000
#define LOOKBACK_HT_ELEMS 0x20202
#define LOOKBACK_WORDS 0x20202
typedef struct HTEntry {
uint32_t key;
uint32_t pos;
} HTEntry;
static void ht_init(HTEntry *ht)
{
for (size_t i = 0; i < LOOKBACK_HT_ELEMS; i++) {
ht[i].pos = -1;
}
}
static uint32_t ht_lookup_and_upsert(HTEntry *ht, const AVCRC *hash_ctx,
uint32_t key, uint32_t pos)
{
uint32_t ret = -1;
size_t hash = av_crc(hash_ctx, 0, (uint8_t*)&key, 4) % LOOKBACK_HT_ELEMS;
for (size_t i = hash; i < hash + LOOKBACK_HT_ELEMS; i++) {
size_t wrapped_index = i % LOOKBACK_HT_ELEMS;
HTEntry *entry = &ht[wrapped_index];
if (entry->key == key || entry->pos == -1) {
ret = entry->pos;
entry->key = key;
entry->pos = pos;
break;
}
}
return ret;
}
static void ht_delete(HTEntry *ht, const AVCRC *hash_ctx,
uint32_t key, uint32_t pos)
{
HTEntry *removed_entry = NULL;
size_t removed_hash;
size_t hash = av_crc(hash_ctx, 0, (uint8_t*)&key, 4) % LOOKBACK_HT_ELEMS;
for (size_t i = hash; i < hash + LOOKBACK_HT_ELEMS; i++) {
size_t wrapped_index = i % LOOKBACK_HT_ELEMS;
HTEntry *entry = &ht[wrapped_index];
if (entry->pos == -1)
return;
if (removed_entry) {
size_t candidate_hash = av_crc(hash_ctx, 0, (uint8_t*)&entry->key, 4) % LOOKBACK_HT_ELEMS;
if ((wrapped_index > removed_hash && (candidate_hash <= removed_hash || candidate_hash > wrapped_index)) ||
(wrapped_index < removed_hash && (candidate_hash <= removed_hash && candidate_hash > wrapped_index))) {
*removed_entry = *entry;
entry->pos = -1;
removed_entry = entry;
removed_hash = wrapped_index;
}
} else if (entry->key == key) {
if (entry->pos <= pos) {
entry->pos = -1;
removed_entry = entry;
removed_hash = wrapped_index;
} else {
return;
}
}
}
}
typedef struct DXVEncContext {
AVClass *class;
@ -121,10 +58,8 @@ typedef struct DXVEncContext {
DXVTextureFormat tex_fmt;
int (*compress_tex)(AVCodecContext *avctx);
const AVCRC *crc_ctx;
HTEntry color_lookback_ht[LOOKBACK_HT_ELEMS];
HTEntry lut_lookback_ht[LOOKBACK_HT_ELEMS];
FFHashtableContext *color_ht;
FFHashtableContext *lut_ht;
} DXVEncContext;
/* Converts an index offset value to a 2-bit opcode and pushes it to a stream.
@ -159,27 +94,32 @@ static int dxv_compress_dxt1(AVCodecContext *avctx)
DXVEncContext *ctx = avctx->priv_data;
PutByteContext *pbc = &ctx->pbc;
void *value;
uint32_t color, lut, idx, color_idx, lut_idx, prev_pos, state = 16, pos = 2, op = 0;
uint32_t color, lut, idx, color_idx, lut_idx, prev_pos, state = 16, pos = 0, op = 0;
ht_init(ctx->color_lookback_ht);
ht_init(ctx->lut_lookback_ht);
ff_hashtable_clear(ctx->color_ht);
ff_hashtable_clear(ctx->lut_ht);
bytestream2_put_le32(pbc, AV_RL32(ctx->tex_data));
ff_hashtable_set(ctx->color_ht, ctx->tex_data, &pos);
pos++;
bytestream2_put_le32(pbc, AV_RL32(ctx->tex_data + 4));
ht_lookup_and_upsert(ctx->color_lookback_ht, ctx->crc_ctx, AV_RL32(ctx->tex_data), 0);
ht_lookup_and_upsert(ctx->lut_lookback_ht, ctx->crc_ctx, AV_RL32(ctx->tex_data + 4), 1);
ff_hashtable_set(ctx->lut_ht, ctx->tex_data + 4, &pos);
pos++;
while (pos + 2 <= ctx->tex_size / 4) {
idx = 0;
color_idx = 0;
lut_idx = 0;
color = AV_RL32(ctx->tex_data + pos * 4);
prev_pos = ht_lookup_and_upsert(ctx->color_lookback_ht, ctx->crc_ctx, color, pos);
color_idx = prev_pos != -1 ? pos - prev_pos : 0;
if (ff_hashtable_get(ctx->color_ht, &color, &prev_pos))
color_idx = pos - prev_pos;
ff_hashtable_set(ctx->color_ht, &color, &pos);
if (pos >= LOOKBACK_WORDS) {
uint32_t old_pos = pos - LOOKBACK_WORDS;
uint32_t old_color = AV_RL32(ctx->tex_data + old_pos * 4);
ht_delete(ctx->color_lookback_ht, ctx->crc_ctx, old_color, old_pos);
if (ff_hashtable_get(ctx->color_ht, ctx->tex_data + old_pos * 4, &prev_pos) && prev_pos <= old_pos)
ff_hashtable_delete(ctx->color_ht, ctx->tex_data + old_pos * 4);
}
pos++;
@ -188,13 +128,14 @@ static int dxv_compress_dxt1(AVCodecContext *avctx)
idx = color_idx;
} else {
idx = 0;
prev_pos = ht_lookup_and_upsert(ctx->lut_lookback_ht, ctx->crc_ctx, lut, pos);
lut_idx = prev_pos != -1 ? pos - prev_pos : 0;
if (ff_hashtable_get(ctx->lut_ht, &lut, &prev_pos))
lut_idx = pos - prev_pos;
ff_hashtable_set(ctx->lut_ht, &lut, &pos);
}
if (pos >= LOOKBACK_WORDS) {
uint32_t old_pos = pos - LOOKBACK_WORDS;
uint32_t old_lut = AV_RL32(ctx->tex_data + old_pos * 4);
ht_delete(ctx->lut_lookback_ht, ctx->crc_ctx, old_lut, old_pos);
if (ff_hashtable_get(ctx->lut_ht, ctx->tex_data + old_pos * 4, &prev_pos) && prev_pos <= old_pos)
ff_hashtable_delete(ctx->lut_ht, ctx->tex_data + old_pos * 4);
}
pos++;
@ -306,11 +247,12 @@ static av_cold int dxv_init(AVCodecContext *avctx)
return AVERROR(ENOMEM);
}
ctx->crc_ctx = av_crc_get_table(AV_CRC_32_IEEE);
if (!ctx->crc_ctx) {
av_log(avctx, AV_LOG_ERROR, "Could not initialize CRC table.\n");
return AVERROR_BUG;
}
ret = ff_hashtable_alloc(&ctx->color_ht, sizeof(uint32_t), sizeof(uint32_t), LOOKBACK_HT_ELEMS);
if (ret < 0)
return ret;
ret = ff_hashtable_alloc(&ctx->lut_ht, sizeof(uint32_t), sizeof(uint32_t), LOOKBACK_HT_ELEMS);
if (ret < 0)
return ret;
return 0;
}
@ -321,6 +263,9 @@ static av_cold int dxv_close(AVCodecContext *avctx)
av_freep(&ctx->tex_data);
ff_hashtable_freep(&ctx->color_ht);
ff_hashtable_freep(&ctx->lut_ht);
return 0;
}