svac3: pictures decoded side by side

.github/workflows/ci.yml

@@ -42,14 +42,17 @@ jobs:
           cmake -S . -B build -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_C_COMPILER=clang \
             -DCMAKE_C_FLAGS="-fsanitize=thread -g"
           cmake --build build -j"$(nproc)"
-      - name: Decode every stream on 4 threads
+      - name: Decode every stream on 2 and 4 threads
         env:
           TSAN_OPTIONS: halt_on_error=1
         run: |
           for s in tests/streams/*.svac3; do
+            build/svac3dec -t 2 "$s" /dev/null
             build/svac3dec -t 4 "$s" /dev/null
           done
           build/test_api tests/streams/cv608_synth_1080p_cbr2m.svac3
+          build/test_api -lost tests/streams/cv608_patch4_1080p.svac3
+          build/test_api -lost tests/streams/cv608_smartp_1080p.svac3
 
   fuzz:
     runs-on: ubuntu-24.04
@@ -64,6 +67,11 @@ jobs:
             source/svac3/svac3_inter.c source/svac3/svac3_dec.c source/svac3/svac3_dsp.c \
             source/svac3/svac3_pool.c -lpthread \
             -o fuzz_patch
+          clang $F -DFUZZ_THREADS=3 tests/fuzz/fuzz_patch.c source/svac3/svac3_hls.c \
+            source/svac3/svac3_aec.c source/svac3/svac3_patch.c source/svac3/svac3_recon.c \
+            source/svac3/svac3_loopfilter.c source/svac3/svac3_inter.c source/svac3/svac3_dec.c \
+            source/svac3/svac3_dsp.c source/svac3/svac3_pool.c -lpthread \
+            -o fuzz_frames
       - name: Fuzz the header parser for 60 s
         run: |
           mkdir -p corpus
@@ -76,6 +84,11 @@ jobs:
           head -c 60000 tests/streams/cv608_smartp_1080p.svac3 > corpus_patch/library.svac3
           head -c 60000 tests/streams/cv608_patch4_1080p.svac3 > corpus_patch/patches.svac3
           ./fuzz_patch -max_total_time=60 -max_len=65536 corpus_patch
+      - name: Fuzz the picture threads for 60 s
+        run: |
+          mkdir -p corpus_frames
+          cp corpus_patch/*.svac3 corpus_frames/
+          ./fuzz_frames -max_total_time=60 -max_len=65536 corpus_frames
 
   ffmpeg:
     runs-on: ubuntu-24.04

CMakeLists.txt

@@ -59,6 +59,8 @@ add_test(NAME test_api
          COMMAND test_api ${CMAKE_SOURCE_DIR}/tests/streams/cv608_synth_1080p_cbr2m.svac3)
 add_test(NAME test_api_lost_patch
          COMMAND test_api -lost ${CMAKE_SOURCE_DIR}/tests/streams/cv608_patch4_1080p.svac3)
+add_test(NAME test_api_lost_library
+         COMMAND test_api -lost ${CMAKE_SOURCE_DIR}/tests/streams/cv608_smartp_1080p.svac3)
 add_executable(test_dsp tests/test_dsp.c)
 target_include_directories(test_dsp PRIVATE source/svac3)
 target_link_libraries(test_dsp svac3d)

README.md

@@ -52,10 +52,25 @@ decoded pictures. On the 1080p CBR corpus stream, one core decodes about
 200 pictures a second on a Cortex-X925 and about 110 on a Core i9-13900;
 at high bit rates the entropy decoder, which is serial, sets the pace.
 
-`svac3d_set_threads()` (`svac3dec -t N`, FFmpeg's `-threads`) decodes on
-several threads: one parses while another reconstructs, and the loop
-filters run in bands on all of them. Pictures and their order are the same
-whatever the number; on 2 threads a picture takes about 0.65 of the time.
+`svac3d_set_threads()` (`svac3dec -t N`, FFmpeg's `-threads`) decodes N
+pictures at a time. A P picture waits only for the rows of its reference
+that its motion reaches, as the reference's thread finishes them, and
+each picture has its reconstruction and loop filters follow its parser on
+two threads of its own, so up to three threads per picture are busy.
+Pictures come out in the same order and with the same bits whatever the
+number, up to N pictures later than with one thread; `svac3d_flush()`
+returns the last of them at the end of the stream.
+
+On a Core Ultra 5 245K (six P-cores):
+
+| stream | 1 thread | 2 threads | 4 threads |
+|---|---|---|---|
+| 1080p CBR, 90 pictures | 0.45 s | 0.13 s | 0.13 s |
+| 2560x1440, 295 pictures | 3.25 s | 0.89 s | 0.79 s |
+| 1080p QP 22, 120 pictures, an I picture in six | 1.58 s | 0.76 s | 0.68 s |
+
+Threads cost 10-30% more CPU time than one thread does. Streams with many I
+pictures gain least: nothing overlaps an I picture's entropy decoding.
 
 ## API
 
@@ -65,10 +80,14 @@ whatever the number; on 2 threads a picture takes about 0.65 of the time.
 svac3d_t *d = svac3d_open();
 svac3d_set_threads(d, 4);                         /* optional */
 svac3d_decode(d, buf, len, on_picture, opaque);   /* Annex-B, any whole NAL units */
+svac3d_flush(d, on_picture, opaque);              /* at the end, with threads */
 svac3d_close(d);
 ```
 
 `on_picture` receives each decoded picture, cropped to the display size.
+`svac3d_decode_tag()` gives each picture a value from the buffer its first
+patch came in, which is how the FFmpeg wrapper keeps packet timestamps on
+pictures that come out later.
 
 ## FFmpeg
 

ffmpeg/0001-avcodec-add-SVAC-3.0-decoding-via-libsvac3d.patch

@@ -1,4 +1,4 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From 97083a1788ba49dcda36f32b05c9bfeb922a5ca5 Mon Sep 17 00:00:00 2001
 From: Dmitry Ilyin <d.ilyin@openipc.org>
 Date: Wed, 28 Oct 2026 23:38:39 +0300
 Subject: [PATCH] avcodec: add SVAC 3.0 decoding via libsvac3d
@@ -13,21 +13,21 @@ tool set of the GB/T SVAC 3.0 draft.
  libavcodec/allcodecs.c    |   1 +
  libavcodec/codec_desc.c   |   7 ++
  libavcodec/codec_id.h     |   1 +
- libavcodec/libsvac3d.c    | 206 ++++++++++++++++++++++++++++++++++++++
+ libavcodec/libsvac3d.c    | 251 ++++++++++++++++++++++++++++++++++++++
  libavcodec/parsers.c      |   1 +
- libavcodec/svac3.h        |  56 +++++++++++
- libavcodec/svac3_parser.c | 121 ++++++++++++++++++++++
+ libavcodec/svac3.h        |  56 +++++++++
+ libavcodec/svac3_parser.c | 121 ++++++++++++++++++
  libavformat/Makefile      |   1 +
  libavformat/allformats.c  |   1 +
- libavformat/svac3dec.c    |  64 ++++++++++++
- 12 files changed, 466 insertions(+)
+ libavformat/svac3dec.c    |  64 ++++++++++
+ 12 files changed, 511 insertions(+)
  create mode 100644 libavcodec/libsvac3d.c
  create mode 100644 libavcodec/svac3.h
  create mode 100644 libavcodec/svac3_parser.c
  create mode 100644 libavformat/svac3dec.c
 
 diff --git a/configure b/configure
-index 374bd5c..6fd5725 100755
+index 374bd5c..61c7b77 100755
 --- a/configure
 +++ b/configure
 @@ -290,6 +290,7 @@ External library support:
@@ -59,7 +59,7 @@ index 374bd5c..6fd5725 100755
  enabled libtwolame        && require libtwolame twolame.h twolame_init -ltwolame &&
                               { check_lib libtwolame twolame.h twolame_encode_buffer_float32_interleaved -ltwolame ||
                                 die "ERROR: libtwolame must be installed and version must be >= 0.3.10"; }
-+enabled libsvac3d         && require_pkg_config libsvac3d "libsvac3d >= 0.2.0" svac3d.h svac3d_set_threads
++enabled libsvac3d         && require_pkg_config libsvac3d "libsvac3d >= 0.3.0" svac3d.h svac3d_flush
  enabled libuavs3d         && require_pkg_config libuavs3d "uavs3d >= 1.1.41" uavs3d.h uavs3d_decode
  enabled libv4l2           && require_pkg_config libv4l2 libv4l2 libv4l2.h v4l2_ioctl
  enabled libvidstab        && require_pkg_config libvidstab "vidstab >= 0.98" vid.stab/libvidstab.h vsMotionDetectInit
@@ -127,10 +127,10 @@ index 668a068..a089876 100644
      AV_CODEC_ID_FIRST_AUDIO = 0x10000,     ///< A dummy id pointing at the start of audio codecs
 diff --git a/libavcodec/libsvac3d.c b/libavcodec/libsvac3d.c
 new file mode 100644
-index 0000000..e69d957
+index 0000000..94f44cb
 --- /dev/null
 +++ b/libavcodec/libsvac3d.c
-@@ -0,0 +1,206 @@
+@@ -0,0 +1,251 @@
 +/*
 + * This file is part of FFmpeg.
 + *
@@ -163,11 +163,25 @@ index 0000000..e69d957
 +#include "codec_internal.h"
 +#include "decode.h"
 +
++/* The timing of a packet, found again by the tag its pictures carry. A
++ * picture is out at most a few pictures after its packet, so one this many
++ * packets back (after a run of packets with no picture, or with pictures
++ * in error) is not needed any more. */
++#define MAX_PROPS 256
++
++typedef struct PacketProps {
++    int64_t tag;
++    int64_t pts, dts, duration;
++} PacketProps;
++
 +typedef struct LibSVAC3DContext {
 +    svac3d_t *dec;
 +    AVCodecContext *avctx;
 +    AVPacket *pkt;
 +    AVFifo *frames;          ///< decoded pictures not yet returned, AVFrame *
++    AVFifo *props;           ///< PacketProps of the packets pictures may still come from
++    int64_t tag;             ///< of the last packet decoded
++    int drained;             ///< the pictures still in flight at EOF are out
 +    int err;                 ///< error raised inside the output callback
 +    int pending_err;         ///< error to return once the queued pictures are out
 +} LibSVAC3DContext;
@@ -221,6 +235,18 @@ index 0000000..e69d957
 +        av_image_copy_plane(frame->data[i], frame->linesize[i],
 +                            pic->data[i], pic->linesize[i], w, h);
 +    }
++    /* with threads a picture comes out some packets after its own: its
++     * timing is that of the packet its tag names, not the last one */
++    for (PacketProps p; av_fifo_peek(s->props, &p, 1, 0) >= 0; av_fifo_drain2(s->props, 1)) {
++        if (p.tag < pic->tag)
++            continue;
++        if (p.tag == pic->tag) {
++            frame->pts      = p.pts;
++            frame->pkt_dts  = p.dts;
++            frame->duration = p.duration;
++        }
++        break;
++    }
 +    frame->pict_type = pic->pict_type == 1 ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;
 +    if (pic->pict_type == 1)
 +        frame->flags |= AV_FRAME_FLAG_KEY;
@@ -248,8 +274,9 @@ index 0000000..e69d957
 +    s->avctx  = avctx;
 +    s->pkt    = av_packet_alloc();
 +    s->frames = av_fifo_alloc2(2, sizeof(AVFrame *), AV_FIFO_FLAG_AUTO_GROW);
++    s->props  = av_fifo_alloc2(8, sizeof(PacketProps), AV_FIFO_FLAG_AUTO_GROW);
 +    s->dec    = svac3d_open();
-+    if (!s->pkt || !s->frames || !s->dec)
++    if (!s->pkt || !s->frames || !s->props || !s->dec)
 +        return AVERROR(ENOMEM);
 +    avctx->pix_fmt = AV_PIX_FMT_YUV420P;
 +    /* libsvac3d runs its own threads: 0 asks for one per CPU */
@@ -273,6 +300,7 @@ index 0000000..e69d957
 +
 +    drop_frames(s);
 +    av_fifo_freep2(&s->frames);
++    av_fifo_freep2(&s->props);
 +    av_packet_free(&s->pkt);
 +    svac3d_close(s->dec);
 +    s->dec = NULL;
@@ -284,7 +312,9 @@ index 0000000..e69d957
 +    LibSVAC3DContext *s = avctx->priv_data;
 +
 +    drop_frames(s);
++    av_fifo_reset2(s->props);
 +    s->pending_err = 0;
++    s->drained = 0;
 +    svac3d_reset(s->dec);
 +}
 +
@@ -308,11 +338,26 @@ index 0000000..e69d957
 +        }
 +
 +        ret = ff_decode_get_packet(avctx, s->pkt);
-+        if (ret < 0)
-+            return ret;                     /* EAGAIN, or EOF: no pictures are held back */
-+        s->err = 0;
-+        ret = svac3d_decode(s->dec, s->pkt->data, s->pkt->size, svac3d_output, s);
-+        av_packet_unref(s->pkt);
++        if (ret == AVERROR_EOF && !s->drained) {
++            /* the pictures other threads are still decoding */
++            s->drained = 1;
++            s->err = 0;
++            ret = svac3d_flush(s->dec, svac3d_output, s);
++        } else if (ret < 0) {
++            return ret;
++        } else {
++            const PacketProps p = {
++                .tag = ++s->tag, .pts = s->pkt->pts, .dts = s->pkt->dts,
++                .duration = s->pkt->duration,
++            };
++            if (av_fifo_can_read(s->props) >= MAX_PROPS)
++                av_fifo_drain2(s->props, 1);
++            s->err = av_fifo_write(s->props, &p, 1);
++            if (s->err >= 0)
++                ret = svac3d_decode_tag(s->dec, s->pkt->data, s->pkt->size, p.tag,
++                                        svac3d_output, s);
++            av_packet_unref(s->pkt);
++        }
 +        if (s->err < 0) {
 +            s->pending_err = s->err;
 +        } else if (ret < 0) {
@@ -333,7 +378,7 @@ index 0000000..e69d957
 +    .close          = libsvac3d_close,
 +    .flush          = libsvac3d_flush,
 +    FF_CODEC_RECEIVE_FRAME_CB(libsvac3d_receive_frame),
-+    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_OTHER_THREADS,
++    .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_DELAY | AV_CODEC_CAP_OTHER_THREADS,
 +    .caps_internal  = FF_CODEC_CAP_INIT_CLEANUP | FF_CODEC_CAP_AUTO_THREADS,
 +    .p.wrapper_name = "libsvac3d",
 +};