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ffmpeg_debug_qp

Build status

Authors: Werner Robitza, Steve Göring, Pierre Lebreton, Nathan Trevivian

ffmpeg-debug-qp is based on ffmpeg and prints QP values of a video input on a per-frame, per-macroblock basis to STDERR.

The tool comes with an additional Python parser to help interpret the output.

Contents:

Requirements

  • Python 3.6 or higher
  • ffmpeg v4 libraries (⚠️ ffmpeg v5 API is not supported yet, PRs are welcome!)

Linux

For building:

  • libavdevice, libavformat, libavfilter, libavcodec, libswresample, libswscale, libavutil
  • C compiler

For example on Ubuntu:

sudo apt -qq update && \
sudo apt install libavdevice-dev libavformat-dev libavfilter-dev libavcodec-dev libswresample-dev libswscale-dev libavutil-dev build-essential pkg-config

Building under Windows

For building:

  • Visual Studio >= 2015 with C/C++ compiler installed with 64 bit support
  • Depending libraries (FFmpeg) are provided along the project, therefore no extra libraries are needed.

macOS

For building:

Then:

brew install ffmpeg pkg-config

Building

In order to use this tool, you need to build the ffmpeg_debug_qp binary.

For Windows, you can use the pre-built binary for the master branch, which can be found here: https://ci.appveyor.com/api/projects/slhck/ffmpeg-debug-qp/artifacts/build.zip). Also download the DLL files from build/dll.zip and unzip them.

Building under Linux and macOS

Simply run the command:

make

The binary will be created under ffmpeg_debug_qp in the same folder.

You can add it to your $PATH, e.g. by copying it to /usr/local/bin:

sudo cp ./ffmpeg_debug_qp /usr/local/bin/

This way, you can call it from anywhere on your system.

Building under Windows

  • Open the solution file ffmpeg-debug-qp.sln which can be found in build\ffmpeg-debug-qp\
  • Make sure to compile in release mode (See the dropdown on the top menu bar. This is not necessary per-se, but beneficial for speed at runtime)
  • Build the tool with Ctrl-Shift-B
  • The binary will be available in build\bin\, required DLL files can be found in the 7zip archive which can be found in build\bin.7z
  • Copy DLL and binary to the root of the folder ffmpeg-debug-qp so depending scripts can find the binary.

Usage

Run this tool on any of the supported file types:

  • MPEG-2
  • MPEG-4 Part 2
  • H.264 / MPEG-4 Part 10 (AVC)

Supported formats:

  • MPEG-4 Part 14
  • H.264 Annex B bytestreams

Direct Usage

Simply call the binary with the path to a file:

./ffmpeg_debug_qp test/test.mp4
[h264 @ 0x7fa9c780d200] nal_unit_type: 5(IDR), nal_ref_idc: 3
[h264 @ 0x7fa9c780d200] Format yuv420p chosen by get_format().
[h264 @ 0x7fa9c780d200] Reinit context to 320x192, pix_fmt: yuv420p
[h264 @ 0x7fa9c780d200] New frame, type: I
[h264 @ 0x7fa9c780d200] 1111111111111111111111111111111111111111
[h264 @ 0x7fa9c780d200] 1111111111111111111111111111111111111111
[h264 @ 0x7fa9c780d200] 1111111111111111111111111111111111111111
[h264 @ 0x7fa9c780d200] 1111111111111111111111111111111111111111
[h264 @ 0x7fa9c780d200] 1111111111111111111111111111111111111111
[h264 @ 0x7fa9c780d200] 1111111111111111111111111111111111111111

You will see the QP values for each macroblock of every frame. Each pair of two numbers is a QP value, hence, in the above example, the QP values are 11, 11 and so on.

Python Usage

You can run the supplied Python tool that helps you parse the results from ffmpeg_debug_qp.

First, build the binary and add it to your $PATH.

You can run the library directly via python3 -m ffmpeg_debug_qp_parser, or install it with pip:

pip3 install --user ffmpeg_debug_qp_parser

The tool options are as follows:

usage: ffmpeg_debug_qp_parser [-h] [-f] [-of OUTPUT_FORMAT] [-p PATH_TO_TOOL] [-l | -k]
                              [-m | -a]
                              video|logfile output

Parse QP values from ffmpeg-debug-qp

positional arguments:
  video|logfile         Video file to generate output for, or existing logfile
  output                Output file

optional arguments:
  -h, --help            show this help message and exit
  -f, --force           Overwrite output
  -of OUTPUT_FORMAT, --output-format OUTPUT_FORMAT
                        Output format, one of: ld-json (default), json or csv
  -p PATH_TO_TOOL, --path-to-tool PATH_TO_TOOL
                        Path to ffmpeg_debug_qp executable (will search in $PATH by default)
  -l, --use-logfile     Use precalculated logfile instead of the video
  -k, --keep-logfile    Don't remove the temporary logfile 'video.debug'
  -m, --include-macroblock-data
                        Include macroblock-level data, such as: type, interlaced and segmentation
  -a, --compute-averages-only
                        Only compute the frame-average QPs

Python Example

To run a basic example:

ffmpeg_debug_qp_parser input.mp4 output_file.json -m -of json

This reads the file input.mp4 and produces a JSON file output_file.json, with a list of frames and each of their macroblocks in the format:

  [
      {
          "frameType": "I",
          "frameSize": 7787,
          "qpAvg": 26.87280701754386,
          "qpValues": [
              {
                  "qp": 25,
                  "type": "i",
                  "segmentation": "",
                  "interlaced": ""
              },
              {
                  "qp": 26,
                  "type": "i",
                  "segmentation": "",
                  "interlaced": ""
              }, ...

The frame and macroblock types are as per ffmpeg debug information. The same goes for segmentation and interlaced values.

For example outputs, see:

Acknowledgement

This code is based on:

  • the code from Fredrik Pihl
  • which is adapted from the code example demuxing_decoding.c by Stefano Sabatini

See also this thread on the libav-user mailing list.

Test video part of Big Buck Bunny (c) copyright 2008, Blender Foundation / www.bigbuckbunny.org

License

MIT License

Copyright (c) 2016-2021 Werner Robitza, Steve Göring, Fredrik Pihl, Stefano Sabatini, Nathan Trevivian

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

FFmpeg libraries are licensed under the GNU Lesser General Public License, version 2.1.