video editing include change resolution and length using R and Python

Original video:

Video

Code

library(tidyverse)
library(av)

check video resolution

Code

get_video_resolution_ffmpeg <- function(file_path) {
  if (!file.exists(file_path)) {
    stop("File does not exist.")
  }
  # Run ffmpeg command and capture output
  cmd <- sprintf("ffmpeg -i %s 2>&1", shQuote(normalizePath(file_path)))
  output <- system(cmd, intern = TRUE, ignore.stderr = FALSE)
  # Find the line containing video stream details
  video_line <- grep("Video:", output, value = TRUE)
  if (length(video_line) == 0) {
    stop("No video stream found.")
  }
  # Extract resolution using regex (e.g., 1920x1080)
  resolution <- regmatches(video_line, regexpr("\\d{3,}x\\d{3,}", video_line))
  if (length(resolution) == 0) {
    stop("Resolution not detected.")
  }
  dimensions <- as.numeric(strsplit(resolution, "x")[[1]])
  return(dimensions)
}

Code

resolution <- get_video_resolution_ffmpeg("demo.mp4")
cat(sprintf("Resolution: %dx%d", resolution[1], resolution[2]))

Resolution: 960x720

check video length and size

Code

video_info <- av::av_media_info("demo.mp4")
video_length <- video_info$duration
cat("video length:",video_length)

video length: 30.02501

Code

video_size_mb <- file.info("demo.mp4")$size / (1024^2)
cat("video size in mb:",video_size_mb)

video size in mb: 1.029325

change video resolution

Code

# Input video file path
input_video <- "demo.mp4"

# Output video file path
output_video <- "demo_resolution.mp4"

# Desired width and height
new_width <- 960/3*2
new_height <- 720/3*2

# Construct the FFmpeg command for resizing
ffmpeg_command <- paste0(
  "ffmpeg -i '", input_video, "' -vf scale=", new_width, ":", new_height, " '", output_video, "'"
)

# Execute the FFmpeg command
system(ffmpeg_command)

cat("Video resized to", new_width, "x", new_height, "and saved to", output_video, "\n")

Video resized to 640 x 480 and saved to demo_resolution.mp4

Video after change resolution:

Code

resolution <- get_video_resolution_ffmpeg(output_video)
cat(sprintf("Resolution: %dx%d", resolution[1], resolution[2]))

Resolution: 640x480

Code

video_info <- av::av_media_info(output_video)
video_length <- video_info$duration
cat("video length:",video_length)

video length: 30.02501

Code

video_size_mb <- file.info(output_video)$size / (1024^2)
cat("video size in mb:",video_size_mb)

video size in mb: 0.72155

change length of video

Code

# Define input/output files and timestamps
input_file <- "demo.mp4"

# Define input and output file paths
input_video <- "demo.mp4"
output_video <- "demo_change_length.mp4"

# --- Example 1: Trimming from the beginning ---
start_time <- "00:00:05" # Start at 5 seconds
duration <- "00:00:10"  # Keep for 10 seconds

command_trim <- sprintf("ffmpeg -i %s -ss %s -t %s  %s",
                        input_video, start_time, duration, output_video)

#command_trim
system(command_trim)
cat(paste("Trimmed video saved to:", output_video, "\n"))

Trimmed video saved to: demo_change_length.mp4

Video after change length:

Code

video_info <- av::av_media_info("demo_change_length.mp4")
video_length <- video_info$duration
cat("video length:",video_length)

video length: 10

Code

video_size_mb <- file.info("demo_change_length.mp4")$size / (1024^2)
cat("video size in mb:",video_size_mb)

video size in mb: 0.275506

video Crop

Code

# Define the path to the input video file
input_video_path <- "demo.mp4"  # Replace with your video file path

# Define the path to save the cropped video
output_video_path <- "demo_crop.mp4"  # Replace with your desired output path

# Define crop parameters
crop_width <- 640   # Desired width of the cropped video
crop_height <- 360  # Desired height of the cropped video
crop_x <- 100       # X offset for cropping
crop_y <- 50        # Y offset for cropping

# Define the crop filter
crop_filter <- sprintf("crop=%d:%d:%d:%d", crop_width, crop_height, crop_x, crop_y)

# Crop the video
av::av_encode_video(
  input = input_video_path,
  output = output_video_path,
  vfilter = crop_filter,
  audio=input_video_path
)

[1] "/Users/jinchaoduan/Documents/Project/Tech-blog/posts/video/demo_crop.mp4"

Code

cat("Video cropped successfully and saved to:", output_video_path, "\n")

Video cropped successfully and saved to: demo_crop.mp4

Video after crop:

video to image

Code

# Convert MP4 to images (frames)
av_video_images(
  video = "demo.mp4", 
  destdir = "output_img",  # Save frames as PNG files
  format = "jpg",
  fps = 1  # Extract 1 frame per second (adjust FPS as needed)
)

 [1] "output_img/image_000001.jpg" "output_img/image_000002.jpg"
 [3] "output_img/image_000003.jpg" "output_img/image_000004.jpg"
 [5] "output_img/image_000005.jpg" "output_img/image_000006.jpg"
 [7] "output_img/image_000007.jpg" "output_img/image_000008.jpg"
 [9] "output_img/image_000009.jpg" "output_img/image_000010.jpg"
[11] "output_img/image_000011.jpg" "output_img/image_000012.jpg"
[13] "output_img/image_000013.jpg" "output_img/image_000014.jpg"
[15] "output_img/image_000015.jpg" "output_img/image_000016.jpg"
[17] "output_img/image_000017.jpg" "output_img/image_000018.jpg"
[19] "output_img/image_000019.jpg" "output_img/image_000020.jpg"
[21] "output_img/image_000021.jpg" "output_img/image_000022.jpg"
[23] "output_img/image_000023.jpg" "output_img/image_000024.jpg"
[25] "output_img/image_000025.jpg" "output_img/image_000026.jpg"
[27] "output_img/image_000027.jpg" "output_img/image_000028.jpg"
[29] "output_img/image_000029.jpg" "output_img/image_000030.jpg"

convert mp4 to mp3

Code

# Define the path to the input MP4 file
input_video_path <- "demo.mp4"  # Replace with the path to your MP4 file

# Define the path to save the output MP3 file
output_audio_path <- "demo.mp3"  # Replace with the desired output path for the MP3 file

# Convert MP4 to MP3
av::av_audio_convert(input_video_path,output_audio_path)

[1] "/Users/jinchaoduan/Documents/Project/Tech-blog/posts/video/demo.mp3"

Code

cat("Conversion complete! MP3 saved to:", output_audio_path, "\n")

Conversion complete! MP3 saved to: demo.mp3

Audio

Code

library(av)

Changing lengto of mp3

Code

video_info=av::av_media_info("demo.mp3" )
video_info$duration

[1] 30.04082

Code

pcm_data <- read_audio_bin("demo.mp3" , channels = 1, end_time = 2.0)
plot(pcm_data, type = 'l')

Code

start_time <- 2 # Start at 1 seconds
total_time <- 4  # Keep for 10 seconds

av_audio_convert(audio="demo.mp3",output="demo_cut.mp3",start_time=start_time,total_time=total_time)

[1] "/Users/jinchaoduan/Documents/Project/Tech-blog/posts/video/demo_cut.mp3"

Code

video_info=av::av_media_info("demo_cut.mp3")
video_info$duration

[1] 4.101224