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Merged
merged 11 commits into from
Apr 11, 2025
Merged

Move sample rate and sample format conversion utils into FFMPEGCommon.cpp #629

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7921558
Disable FFmpeg logs for encoder
NicolasHug Apr 7, 2025
2a19014
Merge branch 'main' of github.com:pytorch/torchcodec into loglevelenc…
NicolasHug Apr 8, 2025
73bdc85
Use c++ strings
NicolasHug Apr 8, 2025
54f5543
Merge branch 'main' of github.com:pytorch/torchcodec into loglevelenc…
NicolasHug Apr 8, 2025
24842b6
Account for frame_size being 0
NicolasHug Apr 8, 2025
c3ac80a
Merge branch 'main' of github.com:pytorch/torchcodec into encoding_wav
NicolasHug Apr 9, 2025
5b39c8f
WIP
NicolasHug Apr 9, 2025
1f9f904
Move createSwrContext in ffmpeg file
NicolasHug Apr 9, 2025
f525848
WIP
NicolasHug Apr 9, 2025
9150137
Move convertAudioAVFrameSampleFormatAndSampleRate in ffmpeg file
NicolasHug Apr 9, 2025
cf8dd11
revert stuff
NicolasHug Apr 9, 2025
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73 changes: 71 additions & 2 deletions src/torchcodec/_core/FFMPEGCommon.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -116,16 +116,17 @@ void setChannelLayout(
#endif
}

SwrContext* allocateSwrContext(
SwrContext* createSwrContext(
UniqueAVCodecContext& avCodecContext,
AVSampleFormat sourceSampleFormat,
AVSampleFormat desiredSampleFormat,
int sourceSampleRate,
int desiredSampleRate) {
SwrContext* swrContext = nullptr;
int status = AVSUCCESS;
#if LIBAVFILTER_VERSION_MAJOR > 7 // FFmpeg > 4
AVChannelLayout layout = avCodecContext->ch_layout;
auto status = swr_alloc_set_opts2(
status = swr_alloc_set_opts2(
&swrContext,
&layout,
desiredSampleFormat,
Expand Down Expand Up @@ -155,9 +156,77 @@ SwrContext* allocateSwrContext(
#endif

TORCH_CHECK(swrContext != nullptr, "Couldn't create swrContext");
status = swr_init(swrContext);
TORCH_CHECK(
status == AVSUCCESS,
"Couldn't initialize SwrContext: ",
getFFMPEGErrorStringFromErrorCode(status),
". If the error says 'Invalid argument', it's likely that you are using "
"a buggy FFmpeg version. FFmpeg4 is known to fail here in some "
"valid scenarios. Try to upgrade FFmpeg?");
return swrContext;
}

UniqueAVFrame convertAudioAVFrameSampleFormatAndSampleRate(
const UniqueSwrContext& swrContext,
const UniqueAVFrame& srcAVFrame,
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@scotts scotts Apr 11, 2025

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Nit: we should be consistent about src and source. I have a preference for src, as it's a universal abbreviation, particularly when paired with dst. But if we say source in a lot of other places, we should stick with that.

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@scotts scotts Apr 11, 2025

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Double nit, and I recognize this name already existed: convertAudioAVFrameSampleFormatAndSampleRate() is very long, and I feel like we're encoding parameter names that modify the operation into the name. I feel like it's clearer as just convertAudioAVFrame().

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@NicolasHug NicolasHug Apr 11, 2025

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Sounds good, I'll merge as-is and follow-up with a PR to address these

AVSampleFormat desiredSampleFormat,
int sourceSampleRate,
int desiredSampleRate) {
UniqueAVFrame convertedAVFrame(av_frame_alloc());
TORCH_CHECK(
convertedAVFrame,
"Could not allocate frame for sample format conversion.");

setChannelLayout(convertedAVFrame, srcAVFrame);
convertedAVFrame->format = static_cast<int>(desiredSampleFormat);
convertedAVFrame->sample_rate = desiredSampleRate;
if (sourceSampleRate != desiredSampleRate) {
// Note that this is an upper bound on the number of output samples.
// `swr_convert()` will likely not fill convertedAVFrame with that many
// samples if sample rate conversion is needed. It will buffer the last few
// ones because those require future samples. That's also why we reset
// nb_samples after the call to `swr_convert()`.
// We could also use `swr_get_out_samples()` to determine the number of
// output samples, but empirically `av_rescale_rnd()` seems to provide a
// tighter bound.
convertedAVFrame->nb_samples = av_rescale_rnd(
swr_get_delay(swrContext.get(), sourceSampleRate) +
srcAVFrame->nb_samples,
desiredSampleRate,
sourceSampleRate,
AV_ROUND_UP);
} else {
convertedAVFrame->nb_samples = srcAVFrame->nb_samples;
}

auto status = av_frame_get_buffer(convertedAVFrame.get(), 0);
TORCH_CHECK(
status == AVSUCCESS,
"Could not allocate frame buffers for sample format conversion: ",
getFFMPEGErrorStringFromErrorCode(status));

auto numConvertedSamples = swr_convert(
swrContext.get(),
convertedAVFrame->data,
convertedAVFrame->nb_samples,
static_cast<const uint8_t**>(
const_cast<const uint8_t**>(srcAVFrame->data)),
srcAVFrame->nb_samples);
// numConvertedSamples can be 0 if we're downsampling by a great factor and
// the first frame doesn't contain a lot of samples. It should be handled
// properly by the caller.
TORCH_CHECK(
numConvertedSamples >= 0,
"Error in swr_convert: ",
getFFMPEGErrorStringFromErrorCode(numConvertedSamples));

// See comment above about nb_samples
convertedAVFrame->nb_samples = numConvertedSamples;

return convertedAVFrame;
}

void setFFmpegLogLevel() {
auto logLevel = AV_LOG_QUIET;
const char* logLevelEnvPtr = std::getenv("TORCHCODEC_FFMPEG_LOG_LEVEL");
Expand Down
9 changes: 8 additions & 1 deletion src/torchcodec/_core/FFMPEGCommon.h
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Original file line number Diff line number Diff line change
Expand Up @@ -158,13 +158,20 @@ void setChannelLayout(
void setChannelLayout(
UniqueAVFrame& dstAVFrame,
const UniqueAVFrame& srcAVFrame);
SwrContext* allocateSwrContext(
SwrContext* createSwrContext(
UniqueAVCodecContext& avCodecContext,
AVSampleFormat sourceSampleFormat,
AVSampleFormat desiredSampleFormat,
int sourceSampleRate,
int desiredSampleRate);

UniqueAVFrame convertAudioAVFrameSampleFormatAndSampleRate(
const UniqueSwrContext& swrContext,
const UniqueAVFrame& srcAVFrame,
AVSampleFormat desiredSampleFormat,
int sourceSampleRate,
int desiredSampleRate);

// Returns true if sws_scale can handle unaligned data.
bool canSwsScaleHandleUnalignedData();

Expand Down
110 changes: 12 additions & 98 deletions src/torchcodec/_core/SingleStreamDecoder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1345,20 +1345,29 @@ void SingleStreamDecoder::convertAudioAVFrameToFrameOutputOnCPU(
static_cast<AVSampleFormat>(srcAVFrame->format);
AVSampleFormat desiredSampleFormat = AV_SAMPLE_FMT_FLTP;

StreamInfo& streamInfo = streamInfos_[activeStreamIndex_];
int sourceSampleRate = srcAVFrame->sample_rate;
int desiredSampleRate =
streamInfos_[activeStreamIndex_].audioStreamOptions.sampleRate.value_or(
sourceSampleRate);
streamInfo.audioStreamOptions.sampleRate.value_or(sourceSampleRate);

bool mustConvert =
(sourceSampleFormat != desiredSampleFormat ||
sourceSampleRate != desiredSampleRate);

UniqueAVFrame convertedAVFrame;
if (mustConvert) {
if (!streamInfo.swrContext) {
streamInfo.swrContext.reset(createSwrContext(
streamInfo.codecContext,
sourceSampleFormat,
desiredSampleFormat,
sourceSampleRate,
desiredSampleRate));
}

convertedAVFrame = convertAudioAVFrameSampleFormatAndSampleRate(
streamInfo.swrContext,
srcAVFrame,
sourceSampleFormat,
desiredSampleFormat,
sourceSampleRate,
desiredSampleRate);
Expand Down Expand Up @@ -1393,77 +1402,6 @@ void SingleStreamDecoder::convertAudioAVFrameToFrameOutputOnCPU(
}
}

UniqueAVFrame SingleStreamDecoder::convertAudioAVFrameSampleFormatAndSampleRate(
const UniqueAVFrame& srcAVFrame,
AVSampleFormat sourceSampleFormat,
AVSampleFormat desiredSampleFormat,
int sourceSampleRate,
int desiredSampleRate) {
auto& streamInfo = streamInfos_[activeStreamIndex_];

if (!streamInfo.swrContext) {
createSwrContext(
streamInfo,
sourceSampleFormat,
desiredSampleFormat,
sourceSampleRate,
desiredSampleRate);
}

UniqueAVFrame convertedAVFrame(av_frame_alloc());
TORCH_CHECK(
convertedAVFrame,
"Could not allocate frame for sample format conversion.");

setChannelLayout(convertedAVFrame, srcAVFrame);
convertedAVFrame->format = static_cast<int>(desiredSampleFormat);
convertedAVFrame->sample_rate = desiredSampleRate;
if (sourceSampleRate != desiredSampleRate) {
// Note that this is an upper bound on the number of output samples.
// `swr_convert()` will likely not fill convertedAVFrame with that many
// samples if sample rate conversion is needed. It will buffer the last few
// ones because those require future samples. That's also why we reset
// nb_samples after the call to `swr_convert()`.
// We could also use `swr_get_out_samples()` to determine the number of
// output samples, but empirically `av_rescale_rnd()` seems to provide a
// tighter bound.
convertedAVFrame->nb_samples = av_rescale_rnd(
swr_get_delay(streamInfo.swrContext.get(), sourceSampleRate) +
srcAVFrame->nb_samples,
desiredSampleRate,
sourceSampleRate,
AV_ROUND_UP);
} else {
convertedAVFrame->nb_samples = srcAVFrame->nb_samples;
}

auto status = av_frame_get_buffer(convertedAVFrame.get(), 0);
TORCH_CHECK(
status == AVSUCCESS,
"Could not allocate frame buffers for sample format conversion: ",
getFFMPEGErrorStringFromErrorCode(status));

auto numConvertedSamples = swr_convert(
streamInfo.swrContext.get(),
convertedAVFrame->data,
convertedAVFrame->nb_samples,
static_cast<const uint8_t**>(
const_cast<const uint8_t**>(srcAVFrame->data)),
srcAVFrame->nb_samples);
// numConvertedSamples can be 0 if we're downsampling by a great factor and
// the first frame doesn't contain a lot of samples. It should be handled
// properly by the caller.
TORCH_CHECK(
numConvertedSamples >= 0,
"Error in swr_convert: ",
getFFMPEGErrorStringFromErrorCode(numConvertedSamples));

// See comment above about nb_samples
convertedAVFrame->nb_samples = numConvertedSamples;

return convertedAVFrame;
}

std::optional<torch::Tensor> SingleStreamDecoder::maybeFlushSwrBuffers() {
// When sample rate conversion is involved, swresample buffers some of the
// samples in-between calls to swr_convert (see the libswresample docs).
Expand Down Expand Up @@ -1735,30 +1673,6 @@ void SingleStreamDecoder::createSwsContext(
streamInfo.swsContext.reset(swsContext);
}

void SingleStreamDecoder::createSwrContext(
StreamInfo& streamInfo,
AVSampleFormat sourceSampleFormat,
AVSampleFormat desiredSampleFormat,
int sourceSampleRate,
int desiredSampleRate) {
auto swrContext = allocateSwrContext(
streamInfo.codecContext,
sourceSampleFormat,
desiredSampleFormat,
sourceSampleRate,
desiredSampleRate);

auto status = swr_init(swrContext);
TORCH_CHECK(
status == AVSUCCESS,
"Couldn't initialize SwrContext: ",
getFFMPEGErrorStringFromErrorCode(status),
". If the error says 'Invalid argument', it's likely that you are using "
"a buggy FFmpeg version. FFmpeg4 is known to fail here in some "
"valid scenarios. Try to upgrade FFmpeg?");
streamInfo.swrContext.reset(swrContext);
}

// --------------------------------------------------------------------------
// PTS <-> INDEX CONVERSIONS
// --------------------------------------------------------------------------
Expand Down
14 changes: 0 additions & 14 deletions src/torchcodec/_core/SingleStreamDecoder.h
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Original file line number Diff line number Diff line change
Expand Up @@ -287,13 +287,6 @@ class SingleStreamDecoder {
const UniqueAVFrame& avFrame,
torch::Tensor& outputTensor);

UniqueAVFrame convertAudioAVFrameSampleFormatAndSampleRate(
const UniqueAVFrame& srcAVFrame,
AVSampleFormat sourceSampleFormat,
AVSampleFormat desiredSampleFormat,
int sourceSampleRate,
int desiredSampleRate);

std::optional<torch::Tensor> maybeFlushSwrBuffers();

// --------------------------------------------------------------------------
Expand All @@ -310,13 +303,6 @@ class SingleStreamDecoder {
const DecodedFrameContext& frameContext,
const enum AVColorSpace colorspace);

void createSwrContext(
StreamInfo& streamInfo,
AVSampleFormat sourceSampleFormat,
AVSampleFormat desiredSampleFormat,
int sourceSampleRate,
int desiredSampleRate);

// --------------------------------------------------------------------------
// PTS <-> INDEX CONVERSIONS
// --------------------------------------------------------------------------
Expand Down
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