Re: [FFmpeg-devel] [PATCH v5] libavfi/dnn: add LibTorch as one of DNN backend

["Chen, Wenbin" <wenbin.chen-at-intel.com@ffmpeg.org>]

> > -----Original Message-----
> > From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of
> > wenbin.chen-at-intel.com@ffmpeg.org
> > Sent: Monday, March 11, 2024 1:02 PM
> > To: ffmpeg-devel@ffmpeg.org
> > Subject: [FFmpeg-devel] [PATCH v5] libavfi/dnn: add LibTorch as one of DNN
> > backend
> >
> > From: Wenbin Chen <wenbin.chen@intel.com>
> >
> > PyTorch is an open source machine learning framework that accelerates
> > the path from research prototyping to production deployment. Official
> > website: https://pytorch.org/. We call the C++ library of PyTorch as
> > LibTorch, the same below.
> >
> > To build FFmpeg with LibTorch, please take following steps as reference:
> > 1. download LibTorch C++ library in https://pytorch.org/get-started/locally/,
> > please select C++/Java for language, and other options as your need.
> > Please download cxx11 ABI version (libtorch-cxx11-abi-shared-with-deps-
> > *.zip).
> > 2. unzip the file to your own dir, with command
> > unzip libtorch-shared-with-deps-latest.zip -d your_dir
> > 3. export libtorch_root/libtorch/include and
> > libtorch_root/libtorch/include/torch/csrc/api/include to $PATH
> > export libtorch_root/libtorch/lib/ to $LD_LIBRARY_PATH
> > 4. config FFmpeg with ../configure --enable-libtorch --extra-cflag=-
> > I/libtorch_root/libtorch/include --extra-cflag=-
> > I/libtorch_root/libtorch/include/torch/csrc/api/include --extra-ldflags=-
> > L/libtorch_root/libtorch/lib/
> > 5. make
> >
> > To run FFmpeg DNN inference with LibTorch backend:
> > ./ffmpeg -i input.jpg -vf
> > dnn_processing=dnn_backend=torch:model=LibTorch_model.pt -y
> output.jpg
> > The LibTorch_model.pt can be generated by Python with torch.jit.script()
> api.
> > Please note, torch.jit.trace() is not recommanded, since it does not support
> > ambiguous input size.
> 
> Can you provide more detail (maybe a link from pytorch) about the
> libtorch_model.py generation and so we can have a try.
> 


This is a guide from pytorch: 
https://pytorch.org/tutorials/advanced/cpp_export.html
I will add it into commit log.

I didn't find a ready-made torchscript model to download. I'm afraid you'll have to export
the model yourself to test.

> >
> > Signed-off-by: Ting Fu <ting.fu@intel.com>
> > Signed-off-by: Wenbin Chen <wenbin.chen@intel.com>
> > ---
> >  configure                             |   5 +-
> >  libavfilter/dnn/Makefile              |   1 +
> >  libavfilter/dnn/dnn_backend_torch.cpp | 597
> > ++++++++++++++++++++++++++
> >  libavfilter/dnn/dnn_interface.c       |   5 +
> >  libavfilter/dnn_filter_common.c       |  15 +-
> >  libavfilter/dnn_interface.h           |   2 +-
> >  libavfilter/vf_dnn_processing.c       |   3 +
> >  7 files changed, 624 insertions(+), 4 deletions(-)
> >  create mode 100644 libavfilter/dnn/dnn_backend_torch.cpp
> >
> > +static int fill_model_input_th(THModel *th_model, THRequestItem
> *request)
> > +{
> > +    LastLevelTaskItem *lltask = NULL;
> > +    TaskItem *task = NULL;
> > +    THInferRequest *infer_request = NULL;
> > +    DNNData input = { 0 };
> > +    THContext *ctx = &th_model->ctx;
> > +    int ret, width_idx, height_idx, channel_idx;
> > +
> > +    lltask = (LastLevelTaskItem *)ff_queue_pop_front(th_model-
> > >lltask_queue);
> > +    if (!lltask) {
> > +        ret = AVERROR(EINVAL);
> > +        goto err;
> > +    }
> > +    request->lltask = lltask;
> > +    task = lltask->task;
> > +    infer_request = request->infer_request;
> > +
> > +    ret = get_input_th(th_model, &input, NULL);
> > +    if ( ret != 0) {
> > +        goto err;
> > +    }
> > +    width_idx = dnn_get_width_idx_by_layout(input.layout);
> > +    height_idx = dnn_get_height_idx_by_layout(input.layout);
> > +    channel_idx = dnn_get_channel_idx_by_layout(input.layout);
> > +    input.dims[height_idx] = task->in_frame->height;
> > +    input.dims[width_idx] = task->in_frame->width;
> > +    input.data = av_malloc(input.dims[height_idx] * input.dims[width_idx] *
> > +                           input.dims[channel_idx] * sizeof(float));
> > +    if (!input.data)
> > +        return AVERROR(ENOMEM);
> > +    infer_request->input_tensor = new torch::Tensor();
> > +    infer_request->output = new torch::Tensor();
> > +
> > +    switch (th_model->model->func_type) {
> > +    case DFT_PROCESS_FRAME:
> > +        input.scale = 255;
> > +        if (task->do_ioproc) {
> > +            if (th_model->model->frame_pre_proc != NULL) {
> > +                th_model->model->frame_pre_proc(task->in_frame, &input,
> > th_model->model->filter_ctx);
> > +            } else {
> > +                ff_proc_from_frame_to_dnn(task->in_frame, &input, ctx);
> > +            }
> > +        }
> > +        break;
> > +    default:
> > +        avpriv_report_missing_feature(NULL, "model function type %d",
> > th_model->model->func_type);
> > +        break;
> > +    }
> > +    *infer_request->input_tensor = torch::from_blob(input.data,
> > +        {1, 1, input.dims[channel_idx], input.dims[height_idx],
> > input.dims[width_idx]},
> 
> An extra dimension is added to support multiple frames for algorithms
> such as VideoSuperResolution, besides batch size, channel, height and width.
> 
> Let's first support the regular dimension for NCHW/NHWC,  and then
> add support for multiple frames.

OK, I will update it in patch version 6, and submit another patchset to support
multiple frame input.

Thanks for the review.
Wenbin

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