How to calculate the bitrate of a video per second?

This ffprobe command extracts the presentation timestamp (PTS) and size of every video packet from input.mp4, saving it to a CSV file.

-select_streams v - Only select the video stream (v).
-show_packets - Show individual packet-level information.
-show_entries packet=pts_time,size - Only extract the pts_time (when a packet should be shown) and size (packet size in bytes).
-of csv - Output in CSV format.
input.mp4 - Input video file.

The result of this command looks something like:

packet,0.000000,898
packet,0.020854,6929
packet,0.041708,931
packet,0.062563,1204
packet,0.083417,1612
...

The 2nd part of the command is a python script: calc-bitrate.py

with open('packets.csv', newline='') as csvfile: - open the packets.csv file for reading.
time_buckets[second] += size_bytes - Read the params and accumulate the size of packets for that second.
for sec in sorted(time_buckets.keys()): - for each second, calculate the bitrate with: bitrate_kbps = (time_buckets[sec] * 8) / 1000 and print it out.

Example output:

Second	Bitrate (kbps)
0	6164.38
1	10688.25
2	10093.25
3	9780.40
4	6946.49
5	645.37
...

by Elad Gariany <elad@gariany.com>
Updated on: September 15, 2025
tags: #bitrate #encoding #python

# extract the packet size into packets.csv
ffprobe -select_streams v -show_packets -show_entries packet=pts_time,size -of csv input.mp4 > packets.csv

# to calculate the bitrate of each second of video
# write this to calc-bitrate.py
import csv
from collections import defaultdict

# Load packet data from ffprobe output
time_buckets = defaultdict(int)  # key: second (int), value: total size in bytes

with open('packets.csv', newline='') as csvfile:
    reader = csv.reader(csvfile)
    for row in reader:
        if len(row) < 3:
            continue
        pts_time = float(row[1])
        size_bytes = int(row[2])
        second = int(pts_time)  # floor to the second
        time_buckets[second] += size_bytes

# Print bitrate per second
print("Second\tBitrate (kbps)")
for sec in sorted(time_buckets.keys()):
    bitrate_kbps = (time_buckets[sec] * 8) / 1000  # bytes to kilobits
    print(f"{sec}\t{bitrate_kbps:.2f}")

Related Issues not found

Please contact @eladg to initialize the comment