PlotBitrate

FFProbe Bitrate Graph

This project contains a script for plotting the bitrate of an audio or video stream over time. To get the frame bitrate data ffprobe is used from the ffmpeg package. The ffprobe data is streamed to python as xml frame metadata and optionally sorted by frame type. Matplotlib is used to plot the overall bitrate or each frame type on the same graph with lines for the peak and mean bitrates. The resulting bitrate graph can be saved as an image.

Possible outputs are:

• Image types (png, svg, pdf, ...)
• Raw frame data (csv, xml)

Requirements:

• Python >= 3.6
• FFmpeg >= 1.2 with the ffprobe command
• Matplotlib
• PyQt5 or PyQt6 (optional for image file output)

For using the script from source, install the requirements with pip install -r requirements.txt or use the requirements-dev.txt for development purposes.

Installation

pip install plotbitrate

If you encounter the error message qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found. while running plotbitrate, then you may need to install your distribution's libxcb-cursor0 package. If this package is already installed and/or doesn't resolve the issue, then you can try using QT_DEBUG_PLUGINS=1 plotbitrate input.mkv 2>&1 | grep "No such file" to determine if other libraries are missing.

Useful Options

The raw frame data can be stored in an xml file with the option -f xml_raw, which the graph can be plotted from. This is useful if the graph should be shown multiple times with different options, as the source file doesn't need to be scanned again.

The option --downscale (or -d) is useful if the video is very long and an overview of the bitrate fluctuation is sufficient and zooming in is not necessary. This behavior resembles that of the tool "Bitrate Viewer". With this option, videos will be shown as a downscaled graph, meaning not every second is being displayed. Multiple seconds will be grouped together and the max value will be drawn. This downscaling is not applied when viewing individual frame types as this would lead to wrong graphs. This behavior can be adjusted with the --max-display-values option. The default value is 700, meaning that at most 700 individual seconds/bars are drawn.

CSV Output

You may find it useful to save the raw frame data to a CSV file so the frame data can be processed using another tool. This turns plotbitrate into more of a helper tool rather than a visualization tool.

One example may be using gnuplot to show an impulse plot for every single frame split by frame type. Below is an example gnuplot script that mimics an earlier version of plotbitrate.

#!/usr/bin/gnuplot -persist
set datafile separator ","
plot "< awk -F, '{if($3 == \"I\") print}' frames.csv" u 1:2 t "I" w impulses lt rgb "red", \
     "< awk -F, '{if($3 == \"P\") print}' frames.csv" u 1:2 t "P" w impulses lt rgb "green", \
     "< awk -F, '{if($3 == \"B\") print}' frames.csv" u 1:2 t "B" w impulses lt rgb "blue"

The necessary input data can be generated using:

plotbitrate -o frames.csv input.mkv

Usage Examples

Show video stream bitrate in a window with progress.

plotbitrate input.mkv

Show downscaled video stream bitrate in a window.

plotbitrate -d input.mkv

Show video stream bitrate for each frame type in a window.

plotbitrate -t input.mkv

Save video stream bitrate to an SVG file.

plotbitrate -o output.svg input.mkv

Show audio stream bitrate in a window.

plotbitrate -s audio input.mkv

Save raw ffproble frame data as xml file.

plotbitrate -f xml_raw -o frames.xml input.mkv

Show bitrate graph from raw xml.

plotbitrate frames.xml