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Limit CPU video decoder codec support #6352

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5c1c613
Limit CPU video decoder codec support
JanuszL May 18, 2026
3c37290
Update DALI deps and extra version
JanuszL May 25, 2026
d54c8dd
Typo fix
JanuszL May 25, 2026
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2 changes: 1 addition & 1 deletion DALI_DEPS_VERSION
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@@ -1 +1 @@
99d65ba2e8f1e30fffc6978cda805aa630a2255c
6e59c3ea6333fed7948f7146b1ffbb5a7db5e536
2 changes: 1 addition & 1 deletion DALI_EXTRA_VERSION
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@@ -1 +1 @@
21dd6148f0cf4557531d54b810379c681c898e91
7079ceff2aa2ca2e5a6a55d8ea47b459bf41f9b1
3 changes: 2 additions & 1 deletion dali/operators/video/frames_decoder_base.cc
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Expand Up @@ -509,7 +509,8 @@ void FramesDecoderBase::SeekFrame(int frame_id) {
return; // No need to seek
}

if (next_frame_idx_ < 0) {
if (next_frame_idx_ < 0 || (HasIndex() && next_frame_idx_ >= NumFrames())) {
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LOG_LINE << "Resetting decoder because next_frame_idx_ is out of bounds" << std::endl;
Reset();
}
assert(next_frame_idx_ >= 0);
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29 changes: 18 additions & 11 deletions dali/operators/video/frames_decoder_cpu.cc
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Expand Up @@ -50,6 +50,10 @@ void FramesDecoderCpu::Flush() {

bool FramesDecoderCpu::ReadNextFrame(uint8_t *data) {
LOG_LINE << "FramesDecoderCpu::ReadNextFrame: next_frame_idx_=" << next_frame_idx_ << std::endl;
if (next_frame_idx_ == 0) {
// call NumFrames() to populate the index before any frames are read
NumFrames();
}
// No more frames in the file
if (next_frame_idx_ == -1) {
return false;
Expand Down Expand Up @@ -154,19 +158,21 @@ bool FramesDecoderCpu::ReadRegularFrame(uint8_t *data) {
LOG_LINE << (copy_to_output ? "Read" : "Skip") << " frame (ReadRegularFrame), index "
<< next_frame_idx_ << ", timestamp " << std::setw(5) << frame_->pts
<< std::endl;
if (!copy_to_output) {
++next_frame_idx_;
return true;
if (copy_to_output) {
CopyToOutput(data);
}

CopyToOutput(data);
++next_frame_idx_;
if (next_frame_idx_ >= NumFrames()) {
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next_frame_idx_ = -1;
LOG_LINE << "Next frame index out of bounds (regular), setting to -1" << std::endl;
}
return true;
Comment on lines 164 to 169
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@greptile-apps greptile-apps Bot May 18, 2026

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P1 The new EOS guard calls NumFrames() unconditionally on every decoded frame, which can invoke ParseNumFrames() when no index is built and nb_frames is zero in the container. ParseNumFrames() reads all remaining demuxer packets to completion, so the very first frame's increment will exhaust the packet stream and cause all subsequent av_read_frame calls to return EOF — silently dropping every frame after the first. The existing guard in ReadFlushFrame has the same limitation (documented with a TODO) but that function runs only after the demuxer is already exhausted. The fix is to guard the check with HasIndex(), mirroring the SeekFrame condition added in this same PR.

Suggested change
++next_frame_idx_;
if (next_frame_idx_ >= NumFrames()) {
next_frame_idx_ = -1;
LOG_LINE << "Next frame index out of bounds (regular), setting to -1" << std::endl;
}
return true;
++next_frame_idx_;
// TODO(awolant): Figure out how to handle this during index building
// Or when NumFrames is unavailable
if (HasIndex() && next_frame_idx_ >= NumFrames()) {
next_frame_idx_ = -1;
LOG_LINE << "Next frame index out of bounds (regular), setting to -1" << std::endl;
}
return true;

Fix in Claude Code

}

ret = avcodec_send_packet(codec_ctx_, nullptr);
DALI_ENFORCE(ret >= 0,
make_string("Failed to send packet to decoder: ", av_error_string(ret)));
// the decoder has already drained — no more packets to send
DALI_ENFORCE(ret >= 0 || ret == AVERROR_EOF,
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@jantonguirao jantonguirao May 22, 2026

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[Nit/Wording] Now that AVERROR_EOF is accepted as a non-error, the message "Failed to send packet to decoder" is misleading for ret == AVERROR_EOF — except, of course, that branch no longer triggers the ENFORCE. Still, if the ENFORCE does fire, the message reads better as "avcodec_send_packet (flush) failed: ..." so it's clear which call site it is.

More importantly: dropping into flush_state_ = true on AVERROR_EOF is the right thing, but worth a 1-line comment here explaining why EOF is acceptable (the decoder has already drained — no more packets to send) so this doesn't look like accidental error-swallowing.

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@JanuszL JanuszL May 22, 2026

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Added comment

make_string("avcodec_send_packet failed: ", av_error_string(ret)));
flush_state_ = true;

return false;
Expand All @@ -176,6 +182,7 @@ bool FramesDecoderCpu::ReadFlushFrame(uint8_t *data) {
bool copy_to_output = data != nullptr;
if (avcodec_receive_frame(codec_ctx_, frame_) < 0) {
flush_state_ = false;
next_frame_idx_ = -1;
return false;
}

Expand All @@ -189,7 +196,7 @@ bool FramesDecoderCpu::ReadFlushFrame(uint8_t *data) {
++next_frame_idx_;

// TODO(awolant): Figure out how to handle this during index building
// Or when NumFrames in unavailible
// Or when NumFrames in unavailable
if (next_frame_idx_ >= NumFrames()) {
next_frame_idx_ = -1;
LOG_LINE << "Next frame index out of bounds, setting to -1" << std::endl;
Expand All @@ -213,15 +220,15 @@ bool FramesDecoderCpu::SelectVideoStream(int stream_id) {
assert(codec_params_);
AVCodecID codec_id = codec_params_->codec_id;

static constexpr std::array<AVCodecID, 7> codecs = {
AVCodecID::AV_CODEC_ID_H264,
AVCodecID::AV_CODEC_ID_HEVC,
static constexpr std::array<AVCodecID, 3> codecs = {
AVCodecID::AV_CODEC_ID_VP8,
AVCodecID::AV_CODEC_ID_VP9,
AVCodecID::AV_CODEC_ID_MJPEG,
// Those are not supported by our compiled version of libavcodec,
// AVCodecID::AV_CODEC_ID_AV1,
// AVCodecID::AV_CODEC_ID_MPEG4,
// AVCodecID::AV_CODEC_ID_H264,
// AVCodecID::AV_CODEC_ID_HEVC,
};

if (std::find(codecs.begin(), codecs.end(), codec_id) == codecs.end()) {
Expand Down
25 changes: 0 additions & 25 deletions dali/operators/video/frames_decoder_test.cc
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Expand Up @@ -200,24 +200,12 @@ TEST_F(FramesDecoderTest_CpuOnlyTests, ConstantFrameRate) {
RunTest(decoder, cfr_videos_[0]);
}

TEST_F(FramesDecoderTest_CpuOnlyTests, ConstantFrameRateHevc) {
FramesDecoderCpu decoder(cfr_hevc_videos_paths_[0]);
decoder.BuildIndex();
RunTest(decoder, cfr_videos_[0]);
}

TEST_F(FramesDecoderTest_CpuOnlyTests, VariableFrameRate) {
FramesDecoderCpu decoder(vfr_videos_paths_[1]);
decoder.BuildIndex();
RunTest(decoder, vfr_videos_[1]);
}

TEST_F(FramesDecoderTest_CpuOnlyTests, VariableFrameRateHevc) {
FramesDecoderCpu decoder(vfr_hevc_videos_paths_[0]);
decoder.BuildIndex();
RunTest(decoder, vfr_hevc_videos_[0]);
}

TEST_F(FramesDecoderTest_CpuOnlyTests, InvalidSeek) {
FramesDecoderCpu decoder(cfr_videos_paths_[0]);
decoder.BuildIndex();
Expand Down Expand Up @@ -284,13 +272,6 @@ TEST_F(FramesDecoderGpuTest, InMemoryVfrVideo) {
RunTest(decoder, vfr_videos_[0]);
}

TEST_F(FramesDecoderTest_CpuOnlyTests, InMemoryVfrHevcVideo) {
auto memory_video = MemoryVideo(vfr_videos_paths_[0]);
FramesDecoderCpu decoder(memory_video.data(), memory_video.size());
decoder.BuildIndex();
RunTest(decoder, vfr_videos_[0]);
}

TEST_F(FramesDecoderGpuTest, InMemoryVfrHevcVideo) {
if (!FramesDecoderGpu::SupportsHevc()) {
GTEST_SKIP();
Expand All @@ -307,12 +288,6 @@ TEST_F(FramesDecoderTest_CpuOnlyTests, VariableFrameRateNoIndex) {
RunTest(decoder, vfr_videos_[0], false);
}

TEST_F(FramesDecoderTest_CpuOnlyTests, VariableFrameRateHevcNoIndex) {
auto memory_video = MemoryVideo(vfr_hevc_videos_paths_[1]);
FramesDecoderCpu decoder(memory_video.data(), memory_video.size());
RunTest(decoder, vfr_hevc_videos_[1], false);
}

TEST_F(FramesDecoderTest_CpuOnlyTests, NoIndexSeek) {
auto memory_video = MemoryVideo(vfr_videos_paths_[0]);
FramesDecoderCpu decoder(memory_video.data(), memory_video.size());
Expand Down
6 changes: 3 additions & 3 deletions dali/operators/video/input/video_input_test.cc
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Expand Up @@ -228,17 +228,17 @@ class VideoInputNextOutputDataIdTest : public ::testing::Test {
const std::string video_input_name_ = "VIDEO_INPUT";
const std::vector<TestFileDescriptor> test_files_ = {
{
make_string(testing::dali_extra_path(), "/db/video/cfr/test_1.mp4"),
make_string(testing::dali_extra_path(), "/db/video/cfr/test_1_vp9.mp4"),
50,
"there will be cake"
},
{
make_string(testing::dali_extra_path(), "/db/video/cfr/test_2.mp4"),
make_string(testing::dali_extra_path(), "/db/video/cfr/test_2_vp9.mp4"),
60,
"cake is a lie"
},
{
make_string(testing::dali_extra_path(), "/db/video/cfr/test_2.mp4"),
make_string(testing::dali_extra_path(), "/db/video/cfr/test_2_vp9.mp4"),
60,
"" // No data_id for this file.
},
Expand Down
4 changes: 2 additions & 2 deletions dali/operators/video/legacy/reader/video_reader_op_test.cc
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Expand Up @@ -175,7 +175,7 @@ TEST_F(VIDEO_READER_TEST_CLASS, MultipleVideoResolution) {
.AddArg("sequence_length", sequence_length)
.AddArg("random_shuffle", true)
.AddArg("initial_fill", initial_fill)
.AddArg("file_root", std::string{testing::dali_extra_path() + "/db/video_resolution/"})
.AddArg("file_root", std::string{testing::dali_extra_path() + "/db/video_resolution/vp9/"})
.AddOutput("frames", StorageDevice::GPU)
.AddOutput("labels", StorageDevice::GPU));

Expand Down Expand Up @@ -413,7 +413,7 @@ TEST_F(VIDEO_READER_TEST_CLASS, HEVC) {
"Decoder hardware does not support this video codec"
" and/or chroma format";

// richer FFmpeg configuration leads to different behaviour of VFR heuristics so dissable it for
// richer FFmpeg configuration leads to different behaviour of VFR heuristics so disable it for
// this video
pipe.AddOperator(OpSpec(VIDEO_READER_OP_STR)
.AddArg("device", "gpu")
Expand Down
35 changes: 22 additions & 13 deletions dali/operators/video/video_test.cc
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Expand Up @@ -81,24 +81,33 @@ void SaveFrame(uint8_t *frame, int frame_id, int sample_id, int batch_id,

void TestVideo::CompareFrame(int frame_id, const uint8_t *frame, int eps) {
auto &ground_truth = frames_[frame_id];
bool frames_match = true;
// Tolerate a tiny number of isolated subpixel deviations exceeding eps. The CPU VP9
// decode path occasionally produces a single byte that differs by ~32 (suspected SIMD
// glitch in libavcodec/sws_scale that Valgrind cannot instrument). A genuine regression
// produces orders of magnitude more bad subpixels, so this budget still catches real
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@jantonguirao jantonguirao May 22, 2026

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[Question/Design] Tolerating 16 deviating subpixels per frame to mask a suspected libavcodec/sws_scale SIMD glitch is pragmatic, but it does mean a regression that introduces ≤16 wrong subpixels per frame will be silently absorbed. Given the suspected upstream cause, is there any plan to file an upstream bug and/or pin a known-good FFmpeg version, or to scope this tolerance only to the VP9 paths it actually affects (e.g. an extra arg to CompareFrame rather than a global cap)?

Not blocking — the rationale in the comment is clear and the 16/2.7M ratio is tiny — just want to make sure we don't lose the thread on the underlying glitch.

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@JanuszL JanuszL May 22, 2026

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Good point. The threshold is set empirically based on the failures in tests observed. I don't know if there is a good FFmpeg we can pin. I still believe that 16 off pixels is still something we can tolerate, if something is seriously off the number if bigger.

// breakage while suppressing the flake.
static constexpr int max_bad_subpixels = 16;
std::vector<int> bad_per_thread(detail::ThreadCount(), 0);

detail::parallel_for(FrameSize(), detail::ThreadCount(), [&](int start, int end, int id){
int count = 0;
for (int j = start; j < end; ++j) {
if (std::abs(frame[j] - ground_truth.data[j]) > eps) {
frames_match = false;
break;
++count;
}
}
bad_per_thread[id] = count;
});
int total_bad = std::accumulate(bad_per_thread.begin(), bad_per_thread.end(), 0);

if (!frames_match) {
if (total_bad > max_bad_subpixels) {
SaveFrame(const_cast<uint8_t *>(frame), frame_id, 0, 0, "test_frame", Width(),
Height());
SaveFrame(ground_truth.data, frame_id, 0, 0, "ground_truth", Width(),
Height());

FAIL() << "Frames do not match (eps=" << eps
FAIL() << "Frames do not match (eps=" << eps << ", " << total_bad
<< " subpixels exceed threshold, budget=" << max_bad_subpixels
<< "). Debug frames saved to test_frame_*.png and ground_truth_*.png";
}
}
Expand All @@ -125,24 +134,24 @@ void CompareFrameAvgError(int frame_id, size_t frame_size, size_t width, size_t
}

std::vector<std::string> VideoTestBase::cfr_videos_frames_paths_{
testing::dali_extra_path() + "/db/video/cfr/frames_1/",
testing::dali_extra_path() + "/db/video/cfr/frames_2/"};
testing::dali_extra_path() + "/db/video/cfr/frames_1_vp9/",
testing::dali_extra_path() + "/db/video/cfr/frames_2_vp9/"};

std::vector<std::string> VideoTestBase::vfr_videos_frames_paths_{
testing::dali_extra_path() + "/db/video/vfr/frames_1/",
testing::dali_extra_path() + "/db/video/vfr/frames_2/"};
testing::dali_extra_path() + "/db/video/vfr/frames_1_vp9/",
testing::dali_extra_path() + "/db/video/vfr/frames_2_vp9/"};

std::vector<std::string> VideoTestBase::vfr_hevc_videos_frames_paths_{
testing::dali_extra_path() + "/db/video/vfr/frames_1_hevc/",
testing::dali_extra_path() + "/db/video/vfr/frames_2_hevc/"};

std::vector<std::string> VideoTestBase::cfr_videos_paths_{
testing::dali_extra_path() + "/db/video/cfr/test_1.mp4",
testing::dali_extra_path() + "/db/video/cfr/test_2.mp4"};
testing::dali_extra_path() + "/db/video/cfr/test_1_vp9.mp4",
testing::dali_extra_path() + "/db/video/cfr/test_2_vp9.mp4"};

std::vector<std::string> VideoTestBase::vfr_videos_paths_{
testing::dali_extra_path() + "/db/video/vfr/test_1.mp4",
testing::dali_extra_path() + "/db/video/vfr/test_2.mp4"};
testing::dali_extra_path() + "/db/video/vfr/test_1_vp9.mp4",
testing::dali_extra_path() + "/db/video/vfr/test_2_vp9.mp4"};

std::vector<std::string> VideoTestBase::cfr_hevc_videos_paths_{
testing::dali_extra_path() + "/db/video/cfr/test_1_hevc.mp4",
Expand Down
3 changes: 2 additions & 1 deletion dali/test/python/checkpointing/test_dali_checkpointing.py
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Expand Up @@ -855,7 +855,8 @@ def test_experimental_video_reader(
video: VideoConfig,
):
files = [
os.path.join(get_dali_extra_path(), "db", "video", "vfr", f"test_{i}.mp4") for i in (1, 2)
os.path.join(get_dali_extra_path(), "db", "video", "vfr", f"test_{i}_vp9.mp4")
for i in (1, 2)
]

check_reader_checkpointing(
Expand Down
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