Develop Reference

How to specify start and end frames when making a video with ffmpeg

I am working with python in a jupyter notebook, and I am trying to use ffmpeg to specify the start and end images and convert several images from a folder into a single video. I have a folder, 'images', with the images inside labeled, 'image0', 'image1', 'image2', etc. I would like to specify the start and end images in my video. For example, I would like to be able to make the video using 'image100', to 'image200'. Right now, I have:
!/home/jovyan/ffmpeg-dir/ffmpeg -i /home/jovyan/images/image%d.bmp -frames:v 1000 /home/jovyan/output.mp4
This is making the video correctly, but I believe it is just taking the first 1000 images.
Thanks!

Use -start_number.
Use the -start_number option to declare a starting number for the sequence. This is useful if your sequence does not start with img001.jpg but is still in a numerical order.
(source: https://ffmpeg.org/faq.html#toc-How-do-I-encode-single-pictures-into-movies_003f)
For example, I would like to be able to make the video using 'image100', to 'image200'.
You need to combine -start_number 100 and -frames:v 101 (101 frames from image100.jpg to image200.jpg).

You can try this:
ffmpeg -i movie.mp4 -ss 00:00:03 -t 00:00:08 -async 1 cut.mp4
OR
ffmpeg -i movie.mp4 -ss 00:00:03 -t 00:00:08 -async 1 -c copy cut.mp4
The -t option specifies a duration, not an end time. The above command will encode 8s of video starting at 3s. To start at 3s and end at 8s use -t 5. If you are using a current version of ffmpeg you can also replace -t with -to in the above command to end at the specified time.

Programatically add a simple pause to a video

Say I have a 30s video. I want to produce a 40s video that is just the first video but with an extra "freezed" frame (for say 10s) somewhere in the middle of it. (think of it as wanting to comment the video at a specific point)
I know I can do this easily with video editing software. However, I am looking for a command line tool that allows me to do this efficiently (I need to do this several times with variable points to freeze the video)
I am using Python
I thought of using ffmpeg, splitting the video into two, creating a third video composed of a given frame, and then concatenating the three videos.
But maybe there is a much simpler technique?

I found a way to do it
Let's say I have the original movie file: in.mp4
and I want to pause it for 10 seconds with the frame found at the 15s mark
#first extract the frame
ffmpeg -ss 00:00:15 -i in.mp4 -vframes 1 -q:v 2 -y static_frame.png
# Create the movie_aux1.mp4 of the first part of the original video
ffmpeg -t 00:00:15 -i in.mp4 movie_aux1.mp4
# Create the movie_aux2.mp4
ffmpeg -loop 1 -i static_frame.png -t 10 movie_aux2.mp4
# Create the movie_aux3.mp4
ffmpeg -ss 00:00:15 -i in.mp4 movie_aux3.mp4
# Create a list of the movies to concatenate. Dont forget to erase this file afterwards
echo "file 'movie_aux1.mp4'" >> mylist.txt
echo "file 'movie_aux2.mp4'" >> mylist.txt
echo "file 'movie_aux3.mp4'" >> mylist.txt
# Concatenate all three movies
ffmpeg -f concat -safe 0 -i mylist.txt out.mp4

Obtaining scene change frames with corresponding timestamps and scene scored saved in a text file

I have to use FFmpeg to detect shot changes in a video, an also save the timestamps and scores of the detected shot changes? How can i do this with a single command?
EDIT
I jumped to my use case directly, as it was solved directly using FFmpeg, without the need of raw frames.

The best and perfect solution I came across after reading tonnes of Q/A:
Simply use the command:
ffmpeg inputvideo.mp4 -filter_complex "select='gt(scene,0.3)',metadata=print:file=time.txt" -vsync vfr img%03d.png
This will save just the relevant information in the time.txt file like below:
frame:0 pts:108859 pts_time:1.20954
lavfi.scene_score=0.436456
frame:1 pts:285285 pts_time:3.16983
lavfi.scene_score=0.444537
frame:2 pts:487987 pts_time:5.42208
lavfi.scene_score=0.494256
frame:3 pts:904654 pts_time:10.0517
lavfi.scene_score=0.462327
frame:4 pts:2533781 pts_time:28.1531
lavfi.scene_score=0.460413
frame:5 pts:2668916 pts_time:29.6546
lavfi.scene_score=0.432326

FFmpeg create video from images, insert images as frame from timestamp?

So I'm trying to extract every frame of a video, then use ffprobe to see when each frame is played within a video, then be able to stitch that video back together using those extracted images and ffprobe output.
Right now, I have this batch file:
for %%a in (*.mp4) do (
mkdir "%%~na_images" > NUL
ffmpeg.exe -hide_banner -i "%%a" -t 100 "%%~na_images\image-%%d.png"
ffprobe.exe "%%a" -hide_banner -show_entries frame=coded_picture_number,best_effort_timestamp_time -of csv > "%%~na_frames.txt"
)
First, a directory is made for the images.
Then ffmpeg extracts all the frames of the video to individual PNG files, which are numbered appropriately.
Lastly, ffprobe sees when each frame is first shown within that video (IE: frame 1 is shown at 0 seconds, but at say 60fps then frame 2 is played at 0.016667 seconds in the video). The output looks like this:
frame,0.000000,0
frame,0.000000
frame,0.017000,1
frame,0.023220
Where the first number (IE 0.17000 is the time the second frame appears) and the 2nd number is the frame number.
Now my problem is using ffmpeg to take each frame and place it in the proper time within the video. I can do this using another language (probably Python), but my best guess is to make a loop to iterate through the ffprobe output file, get the frame time and image number, place that frame at the points that it appears, then move on to the next frame and time placement. Looking at the frame data I used as an example above, it 'd be something like this:
for line in lines:
mySplit = line.split(',')
# Get image number 0 and insert at time 0.000000
This is the part that I'm not sure how to do in a coding sense. I can read in and parse the lines of the ffprobe output text file, but I have no idea how to insert the frames at certain points in a video using ffmpeg or similar solutions.

You need to tell the system there is more than 1 token. i.e
for /f "tokens=1-4 delims=," %%a in ...
Here you tell it that you want to grab tokens 1 to 4 and delimeter is ,
So for an example of a file containing 1,100,1000,10000 it will assign the %%a to the first token (being 1, and %%b to the second (being 100) etc.

How to compute the number of extra samples added by LAME or FFMPEG

I am attempting to build a MP3 decoder / parser in Python which supports files encoded by LAME or FFMPEG.
My encoding shell script is shown here:
#!/bin/bash
for i in wav/*.wav; do
i=${i##*/};
lame --nores --strictly-enforce-ISO -t --cbr -b 64 -h "wav/${i}" "mpeg/lame/${i%.wav}.mp3";
ffmpeg -i "wav/${i}" -codec:a libmp3lame -qscale:a 2 "mpeg/ffmpeg/${i%.wav}.mp3";
done
This scripts reads WAVE files located in ./wav/ and produces a controlled-bitrate MP3 of 64kbps in my ./mp3/lame/ directory, and a variable-bitrate MP3 of quality 2 in my ./mp3/ffmpeg/.
I have written a Python script that iterates through both resultant MP3s, counting the number of frames and samples. Both the LAME and FFMPEG results are equivalent (in terms of frames and samples), but their binary files are different.
The LAME/FFMPEG sample count was done by iterating through the binary MP3 files, locating and parsing the frame header, then using the MP3 spec to determine the number of samples per frame.
Number of MP3 data-frames: 112 (ignoring the Xing/Info first frame)
Number of output frames: 112*576 = 64512
Here is a comparison of the sample count for a single 4-second input file:
Input WAV # of samples = 62996
Output LAME/FFMPEG # of samples = 64512
Difference = 1516
I understand that according to the LAME FAQ file, resultant MP3 files are zero padded in the front and back to make sure the inverse MDCT is performed properly, but also because the windows overlap.
What I can't ascertain from the above FAQ, or from any previous StackOverflow post, is how to compute the number of artificially added samples. If I can be sure that all 1516 of these samples are zeros, and I can be sure of their position in the bytestream, I'd like to be able to confidently toss them out. Since there are 1516 "extra" samples and there are 576 samples per frame for a V2LIII encoding, then there must be more than two (but less than three) erroneous MPEG frames here.
Is anyone here savvy enough with MPEG encoding/decoding to know how many samples are added, and in which frames those samples will be in? In other words, will the first frame and last frame always contain blank data, or are there more frames?

The easiest way to do this is to decode the resultant MP3s with ffmpeg with loglevel debug mode.
ffmpeg -i file.mp3 -f null - -v 48
Within the console output, you'll have this line
[mp3 # 0000000002be28c0] pad 576 1105
This doesn't include the fixed encoder delay.
So the actual skipped sample count is shown by these two lines
Start padding in first frame:
[mp3 # 0000000002e6bb80] skip 1105/1152 samples
End padding in last frame:
[mp3 # 0000000002e6bb80] discard 576/1152 samples
This info is only present if the Xing header is written.