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Use FrameOutput for audio as well #574

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Merged
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Mar 19, 2025
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Use FrameOutput for audio as well #574

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5 changes: 0 additions & 5 deletions src/torchcodec/decoders/_core/VideoDecoder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -895,10 +895,6 @@ VideoDecoder::AudioFramesOutput VideoDecoder::getFramesPlayedInRangeAudio(
decodeAVFrame([startPts](const UniqueAVFrame& avFrame) {
return startPts < avFrame->pts + getDuration(avFrame);
});
// TODO: it's not great that we are getting a FrameOutput, which is
// intended for videos. We should consider bypassing
// convertAVFrameToFrameOutput and directly call
// convertAudioAVFrameToFrameOutputOnCPU.
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@NicolasHug NicolasHug Mar 18, 2025 •
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So this PR is about not addressing this TODO. I tried to address it, but then realized that we do call convertAVFrameToFrameOutput() in getNextFrameInternal():

torchcodec/src/torchcodec/decoders/_core/VideoDecoder.cpp

Lines 583 to 589 in b830480

VideoDecoder::FrameOutput VideoDecoder::getNextFrameInternal(
std::optional<torch::Tensor> preAllocatedOutputTensor) {
validateActiveStream();
UniqueAVFrame avFrame = decodeAVFrame(
[this](const UniqueAVFrame& avFrame) { return avFrame->pts >= cursor_; });
return convertAVFrameToFrameOutput(avFrame, preAllocatedOutputTensor);
}

If we were to address the TODO, we would need separated audio/video logics in getNextFrameInternal(): one calling convertAVFrameToFrameOutput() (for video), and the other calling the audio-conversion stuff.

And we can't get around the fact that getNextFrameInternal() returns a FrameOutput, can we?

So, I guess this PR is about accepting FrameOutput as a "universal frame output", for both audio and videos.

auto frameOutput = convertAVFrameToFrameOutput(avFrame);
firstFramePtsSeconds =
std::min(firstFramePtsSeconds, frameOutput.ptsSeconds);
Expand Down Expand Up @@ -1163,7 +1159,6 @@ VideoDecoder::FrameOutput VideoDecoder::convertAVFrameToFrameOutput(
std::optional<torch::Tensor> preAllocatedOutputTensor) {
// Convert the frame to tensor.
FrameOutput frameOutput;
frameOutput.streamIndex = activeStreamIndex_;
auto& streamInfo = streamInfos_[activeStreamIndex_];
frameOutput.ptsSeconds = ptsToSeconds(
avFrame->pts, formatContext_->streams[activeStreamIndex_]->time_base);
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8 changes: 6 additions & 2 deletions src/torchcodec/decoders/_core/VideoDecoder.h
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Expand Up @@ -153,9 +153,13 @@ class VideoDecoder {
// They are the equivalent of the user-facing Frame and FrameBatch classes in
// Python. They contain RGB decoded frames along with some associated data
// like PTS and duration.
// FrameOutput is also relevant for audio decoding, typically as the output of
// getNextFrame(), or as a temporary output variable.
struct FrameOutput {
torch::Tensor data; // 3D: of shape CHW or HWC.
int streamIndex;
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Driveby: removing unused streamIndex field

// data shape is:
// - 3D (C, H, W) or (H, W, C) for videos
// - 2D (numChannels, numSamples) for audio
torch::Tensor data;
double ptsSeconds;
double durationSeconds;
};
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5 changes: 4 additions & 1 deletion test/decoders/test_ops.py
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Expand Up @@ -650,12 +650,15 @@ def test_next(self, asset):
frame_index = 0
while True:
try:
frame, *_ = get_next_frame(decoder)
frame, pts_seconds, duration_seconds = get_next_frame(decoder)
except IndexError:
break
torch.testing.assert_close(
frame, asset.get_frame_data_by_index(frame_index)
)
frame_info = asset.get_frame_info(frame_index)
assert pts_seconds == frame_info.pts_seconds
assert duration_seconds == frame_info.duration_seconds
frame_index += 1

@pytest.mark.parametrize(
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