Ameya Keshava Mallya
d0396f30b3
git-subtree-dir: projects/rocdecode git-subtree-mainline:5d609c1e57git-subtree-split:b0bab07940
97 rader
4.4 KiB
ReStructuredText
97 rader
4.4 KiB
ReStructuredText
.. meta::
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:description: Using rocDecode with the FFMpeg demultiplexer
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:keywords: parse video, parse, rocDecode, AMD, ROCm, FFmpeg demuxer
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********************************************************************
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Using the rocDecode FFmpeg demultiplexer
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********************************************************************
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The rocDecode FFmpeg demultiplexer (demuxer) extracts coded picture data from digital media files.
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To use the rocDecode FFmpeg demuxer , import the ``video_demuxer.h`` header file.
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.. code:: C++
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#include "video_demuxer.h"
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Instantiate a ``VideoDemuxer`` with the path to the video file. The ``GetCodecId`` and ``GetBitDepth`` functions can be used to obtain the video stream's codec ID and bit depth. The ``AVCodec2RocDecVideoCodec`` utility function converts the codec ID returned from the demuxer to its corresponding ``rocDecVideoCodec_enum`` value.
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.. code:: C++
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VideoDemuxer *demuxer;
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demuxer = new VideoDemuxer(input_file_path.c_str());
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rocdec_codec_id = AVCodec2RocDecVideoCodec(demuxer->GetCodecID());
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bit_depth = demuxer->GetBitDepth();
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Call ``Demux`` to extract frame data from the stream:
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.. code:: C++
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demuxer->Demux(&pvideo, &n_video_bytes, &pts);
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The demuxer will demultiplex frames sequentially starting at the beginning of the stream. To start the demultiplexing and decoding process from a different frame, create a seek context that specifies a seek criteria and a seek mode.
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The seek criteria describes whether the demuxer needs to seek to a specific frame or seek to a specific timestamp. The seek mode indicates whether the demuxer should seek to the exact frame or to the previous keyframe.
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The seek criteria is defined by the ``SeekCriteriaEnum`` enum and the seek mode is defined by the ``SeekModeEnum`` enum. Both the ``SeekCriteriaEnum`` and the ``SeekModeEnum`` are defined in ``video_demuxer.h``.
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Set the seek criteria to ``SEEK_CRITERIA_FRAME_NUM`` to seek to a frame or to ``SEEK_CRITERIA_TIME_STAMP`` to seek to a timestamp. Set the seek mode to ``SEEK_MODE_EXACT_FRAME`` to seek to the exact frame or to ``SEEK_MODE_PREV_KEY_FRAME`` to seek to the previous keyframe.
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From |videodecode|_:
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.. code:: C++
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VideoSeekContext video_seek_ctx;
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[...]
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do {
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[...]
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if (seek_criteria == 1 && first_frame) {
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// use VideoSeekContext class to seek to given frame number
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video_seek_ctx.seek_frame_ = seek_to_frame;
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video_seek_ctx.seek_crit_ = SEEK_CRITERIA_FRAME_NUM;
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video_seek_ctx.seek_mode_ = (seek_mode ? SEEK_MODE_EXACT_FRAME : SEEK_MODE_PREV_KEY_FRAME);
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demuxer->Seek(video_seek_ctx, &pvideo, &n_video_bytes);
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pts = video_seek_ctx.out_frame_pts_;
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std::cout << "info: Number of frames that were decoded during seek - " << video_seek_ctx.num_frames_decoded_ << std::endl;
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first_frame = false;
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} else if (seek_criteria == 2 && first_frame) {
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// use VideoSeekContext class to seek to given timestamp
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video_seek_ctx.seek_frame_ = seek_to_frame;
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video_seek_ctx.seek_crit_ = SEEK_CRITERIA_TIME_STAMP;
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video_seek_ctx.seek_mode_ = (seek_mode ? SEEK_MODE_EXACT_FRAME : SEEK_MODE_PREV_KEY_FRAME);
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demuxer->Seek(video_seek_ctx, &pvideo, &n_video_bytes);
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pts = video_seek_ctx.out_frame_pts_;
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std::cout << "info: Duration of frame found after seek - " << video_seek_ctx.out_frame_duration_ << " ms" << std::endl;
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first_frame = false;
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} else {
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demuxer->Demux(&pvideo, &n_video_bytes, &pts);
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}
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[...]
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} while (n_video_bytes);
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Delete the demuxer once demultiplexing is complete.
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.. code:: C++
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delete demuxer;
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.. |videodecode| replace:: ``videodecode.cpp``
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.. _videodecode: https://github.com/ROCm/rocDecode/tree/develop/samples/videoDecode/videodecode.cpp
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.. |videodecoderaw| replace:: ``videodecoderaw.cpp``
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.. _videodecoderaw: https://github.com/ROCm/rocDecode/tree/develop/samples/videoDecodeRaw
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.. |common| replace:: ``common.h``
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.. _common: https://github.com/ROCm/rocDecode/blob/develop/samples/common.h
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.. |apifolder| replace:: ``api`` folder
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.. _apifolder: https://github.com/ROCm/rocDecode/tree/develop/api
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.. |utilsfolder| replace:: ``utils`` folder
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.. _utilsfolder: https://github.com/ROCm/rocDecode/tree/develop/utils
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.. |reconfig_struct| replace:: ``ReconfigParams_t``
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.. _reconfig_struct: https://rocm.docs.amd.com/projects/rocDecode/en/latest/doxygen/html/structReconfigParams__t.html
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