[FFmpeg-devel] [PATCH 2/2] lavc: Add unit test for APV entropy decode
Mark Thompson
sw at jkqxz.net
Mon May 5 23:21:28 EEST 2025
---
libavcodec/Makefile | 1 +
libavcodec/tests/apv.c | 449 ++++++++++++++++++++++++++++++++++++++
tests/fate/libavcodec.mak | 5 +
3 files changed, 455 insertions(+)
create mode 100644 libavcodec/tests/apv.c
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index cae8f3a9f1..77734dff24 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -1329,6 +1329,7 @@ TESTPROGS = avcodec \
jpeg2000dwt \
mathops \
+TESTPROGS-$(CONFIG_APV_DECODER) += apv
TESTPROGS-$(CONFIG_AV1_VAAPI_ENCODER) += av1_levels
TESTPROGS-$(CONFIG_CABAC) += cabac
TESTPROGS-$(CONFIG_GOLOMB) += golomb
diff --git a/libavcodec/tests/apv.c b/libavcodec/tests/apv.c
new file mode 100644
index 0000000000..018674afe7
--- /dev/null
+++ b/libavcodec/tests/apv.c
@@ -0,0 +1,449 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/lfg.h"
+#include "libavutil/random_seed.h"
+
+#include "libavcodec/apv_decode.h"
+#include "libavcodec/apv_dsp.h"
+#include "libavcodec/put_bits.h"
+
+
+// Whole file included here to get internal symbols.
+#include "libavcodec/apv_entropy.c"
+
+
+// As defined in 7.1.4, for testing.
+// Adds a check to limit loop after reading 16 zero bits to avoid
+// getting stuck reading a stream of zeroes forever (this matches
+// the behaviour of the faster version).
+
+static unsigned int apv_read_vlc_spec(GetBitContext *gbc, int k_param)
+{
+ unsigned int symbol_value = 0;
+ int parse_exp_golomb = 1;
+ int k = k_param;
+ int stop_loop = 0;
+
+ if(get_bits1(gbc) == 1) {
+ parse_exp_golomb = 0;
+ } else {
+ if (get_bits1(gbc) == 0) {
+ symbol_value += (1 << k);
+ parse_exp_golomb = 0;
+ } else {
+ symbol_value += (2 << k);
+ parse_exp_golomb = 1;
+ }
+ }
+ if (parse_exp_golomb) {
+ int read_limit = 0;
+ do {
+ if (get_bits1(gbc) == 1) {
+ stop_loop = 1;
+ } else {
+ if (++read_limit == 16)
+ break;
+ symbol_value += (1 << k);
+ k++;
+ }
+ } while (!stop_loop);
+ }
+ if (k > 0)
+ symbol_value += get_bits(gbc, k);
+
+ return symbol_value;
+}
+
+// As defined in 7.2.4, for testing.
+
+static void apv_write_vlc_spec(PutBitContext *pbc,
+ unsigned int symbol_val, int k_param)
+{
+ int prefix_vlc_table[3][2] = {{1, 0}, {0, 0}, {0, 1}};
+
+ unsigned int symbol_value = symbol_val;
+ int val_prefix_vlc = av_clip(symbol_val >> k_param, 0, 2);
+ int bit_count = 0;
+ int k = k_param;
+
+ while (symbol_value >= (1 << k)) {
+ symbol_value -= (1 << k);
+ if (bit_count < 2)
+ put_bits(pbc, 1, prefix_vlc_table[val_prefix_vlc][bit_count]);
+ else
+ put_bits(pbc, 1, 0);
+ if (bit_count >= 2)
+ ++k;
+ ++bit_count;
+ }
+
+ if(bit_count < 2)
+ put_bits(pbc, 1, prefix_vlc_table[val_prefix_vlc][bit_count]);
+ else
+ put_bits(pbc, 1, 1);
+
+ if(k > 0)
+ put_bits(pbc, k, symbol_value);
+}
+
+// Old version of ff_apv_entropy_decode_block, for test comparison.
+
+static int apv_entropy_decode_block(int16_t *restrict coeff,
+ GetBitContext *restrict gbc,
+ APVEntropyState *restrict state)
+{
+ const APVVLCLUT *lut = state->decode_lut;
+
+ // DC coefficient.
+ {
+ int abs_dc_coeff_diff;
+ int sign_dc_coeff_diff;
+ int dc_coeff;
+
+ abs_dc_coeff_diff = apv_read_vlc(gbc, state->prev_k_dc, lut);
+
+ if (abs_dc_coeff_diff > 0)
+ sign_dc_coeff_diff = get_bits1(gbc);
+ else
+ sign_dc_coeff_diff = 0;
+
+ if (sign_dc_coeff_diff)
+ dc_coeff = state->prev_dc - abs_dc_coeff_diff;
+ else
+ dc_coeff = state->prev_dc + abs_dc_coeff_diff;
+
+ if (dc_coeff < APV_MIN_TRANS_COEFF ||
+ dc_coeff > APV_MAX_TRANS_COEFF) {
+ av_log(state->log_ctx, AV_LOG_ERROR,
+ "Out-of-range DC coefficient value: %d "
+ "(from prev_dc %d abs_dc_coeff_diff %d sign_dc_coeff_diff %d)\n",
+ dc_coeff, state->prev_dc, abs_dc_coeff_diff, sign_dc_coeff_diff);
+ return AVERROR_INVALIDDATA;
+ }
+
+ coeff[0] = dc_coeff;
+
+ state->prev_dc = dc_coeff;
+ state->prev_k_dc = FFMIN(abs_dc_coeff_diff >> 1, 5);
+ }
+
+ // AC coefficients.
+ {
+ int scan_pos = 1;
+ int first_ac = 1;
+ int k_run = 0;
+ int k_level = state->prev_k_level;
+
+ do {
+ int coeff_zero_run;
+
+ coeff_zero_run = apv_read_vlc(gbc, k_run, lut);
+
+ if (coeff_zero_run > APV_BLK_COEFFS - scan_pos) {
+ av_log(state->log_ctx, AV_LOG_ERROR,
+ "Out-of-range zero-run value: %d (at scan pos %d)\n",
+ coeff_zero_run, scan_pos);
+ return AVERROR_INVALIDDATA;
+ }
+
+ for (int i = 0; i < coeff_zero_run; i++) {
+ coeff[ff_zigzag_direct[scan_pos]] = 0;
+ ++scan_pos;
+ }
+ k_run = FFMIN(coeff_zero_run >> 2, 2);
+
+ if (scan_pos < APV_BLK_COEFFS) {
+ int abs_ac_coeff_minus1;
+ int sign_ac_coeff;
+ int abs_level, level;
+
+ abs_ac_coeff_minus1 = apv_read_vlc(gbc, k_level, lut);
+ sign_ac_coeff = get_bits(gbc, 1);
+
+ abs_level = abs_ac_coeff_minus1 + 1;
+ if (sign_ac_coeff)
+ level = -abs_level;
+ else
+ level = abs_level;
+
+ if (level < APV_MIN_TRANS_COEFF ||
+ level > APV_MAX_TRANS_COEFF) {
+ av_log(state->log_ctx, AV_LOG_ERROR,
+ "Out-of-range AC coefficient value: %d "
+ "(from k_param %d abs_ac_coeff_minus1 %d sign_ac_coeff %d)\n",
+ level, k_level, abs_ac_coeff_minus1, sign_ac_coeff);
+ }
+
+ coeff[ff_zigzag_direct[scan_pos]] = level;
+
+ k_level = FFMIN(abs_level >> 2, 4);
+ if (first_ac) {
+ state->prev_k_level = k_level;
+ first_ac = 0;
+ }
+
+ ++scan_pos;
+ }
+
+ } while (scan_pos < APV_BLK_COEFFS);
+ }
+
+ return 0;
+}
+
+static void binary(char *buf, uint32_t value, int bits)
+{
+ for (int i = 0; i < bits; i++)
+ buf[i] = (value >> (bits - i - 1) & 1) ? '1' : '0';
+ buf[bits] = '\0';
+}
+
+static int test_apv_read_vlc(void)
+{
+ APVVLCLUT lut;
+ int err = 0;
+
+ ff_apv_entropy_build_decode_lut(&lut);
+
+ // Generate all possible 20 bit sequences (padded with zeroes), then
+ // verify that spec and improved parsing functions get the same result
+ // and consume the same number of bits for each possible k_param.
+
+ for (int k = 0; k <= 5; k++) {
+ for (uint32_t b = 0; b < (1 << 20); b++) {
+ uint8_t buf[8] = {
+ b >> 12,
+ b >> 4,
+ b << 4,
+ 0, 0, 0, 0, 0
+ };
+
+ GetBitContext gbc_test, gbc_spec;
+ unsigned int res_test, res_spec;
+ int con_test, con_spec;
+
+ init_get_bits8(&gbc_test, buf, 8);
+ init_get_bits8(&gbc_spec, buf, 8);
+
+ res_test = apv_read_vlc (&gbc_test, k, &lut);
+ res_spec = apv_read_vlc_spec(&gbc_spec, k);
+
+ con_test = get_bits_count(&gbc_test);
+ con_spec = get_bits_count(&gbc_spec);
+
+ if (res_test != res_spec ||
+ con_test != con_spec) {
+ char str[21];
+ binary(str, b, 20);
+ av_log(NULL, AV_LOG_ERROR,
+ "Mismatch reading %s (%d) with k=%d:\n", str, b, k);
+ av_log(NULL, AV_LOG_ERROR,
+ "Test function result %d consumed %d bits.\n",
+ res_test, con_test);
+ av_log(NULL, AV_LOG_ERROR,
+ "Spec function result %d consumed %d bits.\n",
+ res_spec, con_spec);
+ ++err;
+ if (err > 10)
+ return err;
+ }
+ }
+ }
+
+ return err;
+}
+
+static int random_coeff(AVLFG *lfg)
+{
+ // Geometric distribution of code lengths (1-14 bits),
+ // uniform distribution within codes of the length,
+ // equal probability of either sign.
+ int length = (av_lfg_get(lfg) / (UINT_MAX / 14 + 1));
+ int random = av_lfg_get(lfg);
+ int value = (1 << length) + (random & (1 << length) - 1);
+ if (random & (1 << length))
+ return value;
+ else
+ return -value;
+}
+
+static int random_run(AVLFG *lfg)
+{
+ // Expoenential distrbution of run lengths.
+ unsigned int random = av_lfg_get(lfg);
+ for (int len = 0;; len++) {
+ if (random & (1 << len))
+ return len;
+ }
+ // You rolled zero on a 2^32 sided die; well done!
+ return 64;
+}
+
+static int test_apv_entropy_decode_block(void)
+{
+ // Generate random entropy blocks, code them, then ensure they
+ // decode to the same block with both implementations.
+
+ APVVLCLUT decode_lut;
+ AVLFG lfg;
+ unsigned int seed = av_get_random_seed();
+ av_lfg_init(&lfg, seed);
+
+ av_log(NULL, AV_LOG_INFO, "seed = %u\n", seed);
+
+ ff_apv_entropy_build_decode_lut(&decode_lut);
+
+ for (int t = 0; t < 100; t++) {
+ APVEntropyState state, save_state;
+ int16_t block[64];
+ int16_t block_test1[64];
+ int16_t block_test2[64];
+ uint8_t buffer[1024];
+ PutBitContext pbc;
+ GetBitContext gbc;
+ int bits_written;
+ int pos, run, coeff, level, err;
+ int k_dc, k_run, k_level;
+
+ memset(block, 0, sizeof(block));
+ memset(buffer, 0, sizeof(buffer));
+ init_put_bits(&pbc, buffer, sizeof(buffer));
+
+ // Randomly-constructed state.
+ memset(&state, 0, sizeof(state));
+ state.decode_lut = &decode_lut;
+ state.prev_dc = random_coeff(&lfg);
+ state.prev_k_dc = av_lfg_get(&lfg) % 5;
+ state.prev_k_level = av_lfg_get(&lfg) % 4;
+ save_state = state;
+
+ k_dc = state.prev_k_dc;
+ k_run = 0;
+ k_level = state.prev_k_level;
+
+ coeff = random_coeff(&lfg) / 2;
+ block[ff_zigzag_direct[0]] = state.prev_dc + coeff;
+ apv_write_vlc_spec(&pbc, FFABS(coeff), k_dc);
+ if (coeff != 0)
+ put_bits(&pbc, 1, coeff < 0);
+
+ pos = 1;
+ while (pos < 64) {
+ run = random_run(&lfg);
+ if (pos + run > 64)
+ run = 64 - pos;
+ apv_write_vlc_spec(&pbc, run, k_run);
+ k_run = av_clip(run >> 2, 0, 2);
+ pos += run;
+ if (pos < 64) {
+ coeff = random_coeff(&lfg);
+ level = FFABS(coeff) - 1;
+ block[ff_zigzag_direct[pos]] = coeff;
+ apv_write_vlc_spec(&pbc, level, k_level);
+ put_bits(&pbc, 1, coeff < 0);
+ k_level = av_clip((level + 1) >> 2, 0, 4);
+ ++pos;
+ }
+ }
+ bits_written = put_bits_count(&pbc);
+ flush_put_bits(&pbc);
+
+ // Fill output block with a distinctive error value.
+ for (int i = 0; i < 64; i++)
+ block_test1[i] = -9999;
+ init_get_bits8(&gbc, buffer, sizeof(buffer));
+
+ err = apv_entropy_decode_block(block_test1, &gbc, &state);
+ if (err < 0) {
+ av_log(NULL, AV_LOG_ERROR, "Entropy decode returned error.\n");
+ return 1;
+ } else {
+ int bits_read = get_bits_count(&gbc);
+ if (bits_written != bits_read) {
+ av_log(NULL, AV_LOG_ERROR, "Wrote %d bits but read %d.\n",
+ bits_written, bits_read);
+ return 1;
+ } else {
+ err = 0;
+ for (int i = 0; i < 64; i++) {
+ if (block[i] != block_test1[i])
+ ++err;
+ }
+ if (err > 0) {
+ av_log(NULL, AV_LOG_ERROR, "%d mismatches in output block.\n", err);
+ return err;
+ }
+ }
+ }
+
+ init_get_bits8(&gbc, buffer, sizeof(buffer));
+ memset(block_test2, 0, 64 * sizeof(int16_t));
+
+ err = ff_apv_entropy_decode_block(block_test2, &gbc, &save_state);
+ if (err < 0) {
+ av_log(NULL, AV_LOG_ERROR, "Entropy decode returned error.\n");
+ return 1;
+ } else {
+ int bits_read = get_bits_count(&gbc);
+ if (bits_written != bits_read) {
+ av_log(NULL, AV_LOG_ERROR, "Wrote %d bits but read %d.\n",
+ bits_written, bits_read);
+ return 1;
+ } else {
+ err = 0;
+ for (int i = 0; i < 64; i++) {
+ if (block[i] != block_test2[i])
+ ++err;
+ }
+ if (err > 0) {
+ av_log(NULL, AV_LOG_ERROR, "%d mismatches in output block.\n", err);
+ return err;
+ }
+ }
+ }
+
+ if (state.prev_dc != save_state.prev_dc ||
+ state.prev_k_dc != save_state.prev_k_dc ||
+ state.prev_k_level != save_state.prev_k_level) {
+ av_log(NULL, AV_LOG_ERROR, "Entropy state mismatch.\n");
+ return 1;
+ }
+ }
+
+ return 0;
+}
+
+int main(void)
+{
+ int err;
+
+ err = test_apv_read_vlc();
+ if (err) {
+ av_log(NULL, AV_LOG_ERROR, "Read VLC test failed.\n");
+ return err;
+ }
+
+ err = test_apv_entropy_decode_block();
+ if (err) {
+ av_log(NULL, AV_LOG_ERROR, "Entropy decode block test failed.\n");
+ return err;
+ }
+
+ return 0;
+}
diff --git a/tests/fate/libavcodec.mak b/tests/fate/libavcodec.mak
index ef6e6ec40e..b69ad53f7c 100644
--- a/tests/fate/libavcodec.mak
+++ b/tests/fate/libavcodec.mak
@@ -3,6 +3,11 @@ fate-av1-levels: libavcodec/tests/av1_levels$(EXESUF)
fate-av1-levels: CMD = run libavcodec/tests/av1_levels$(EXESUF)
fate-av1-levels: REF = /dev/null
+FATE_LIBAVCODEC-$(CONFIG_APV_DECODER) += fate-apv-entropy
+fate-apv-entropy: libavcodec/tests/apv$(EXESUF)
+fate-apv-entropy: CMD = run libavcodec/tests/apv$(EXESUF)
+fate-apv-entropy: REF = /dev/null
+
FATE_LIBAVCODEC-yes += fate-avpacket
fate-avpacket: libavcodec/tests/avpacket$(EXESUF)
fate-avpacket: CMD = run libavcodec/tests/avpacket$(EXESUF)
--
2.47.2
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