Does anyone know if it is possible to encode a video using ffmpeg in reverse? (So the resulting video plays in reverse?)
I think I can by generating images for each frame (so a folder of images labelled 1.jpg, 2.jpg etc), then write a script to change the image names, and then re-encode the ivdeo from these files.
Does anyone know of a quicker way?
This is an FLV video.
Thank you
No, it isn't possible using ffmpeg to encode a video in reverse without dumping it to images and then back again. There are a number of guides available online to show you how to do it, notably:
http://ubuntuforums.org/showthread.php?t=1353893
and
https://sites.google.com/site/linuxencoding/ffmpeg-tips
The latter of which follows:
Dump all video frames
$ ffmpeg -i input.mkv -an -qscale 1 %06d.jpg
Dump audio
$ ffmpeg -i input.mkv -vn -ac 2 audio.wav
Reverse audio
$ sox -V audio.wav backwards.wav reverse
Cat video frames in reverse order to FFmpeg as input
$ cat $(ls -r *jpg) | ffmpeg -f image2pipe -vcodec mjpeg -r 25 -i - -i backwards.wav -vcodec libx264 -vpre slow -crf 20 -threads 0 -acodec flac output.mkv
Use mencoder to deinterlace PAL dv and double the frame rate from 25 to 50, then pipe to FFmpeg.
$ mencoder input.dv -of rawvideo -ofps 50 -ovc raw -vf yadif=3,format=i420 -nosound -really-quiet -o - | ffmpeg -vsync 0 -f rawvideo -s 720x576 -r 50 -pix_fmt yuv420p -i - -vcodec libx264 -vpre slow -crf 20 -threads 0 video.mkv
I've created a script for this based on Andrew Stubbs' answer
https://gist.github.com/hfossli/6003302
Can be used like so
./ffmpeg_sox_reverse.sh -i Desktop/input.dv -o test.mp4
New Solution
A much simpler method exists now, simply use the command (adjusting input.mkv and reversed.mkv accordingly):
ffmpeg -i input.mkv -af areverse -vf reverse reversed.mkv
The -af areverse will reverse audio, and -vf reverse will reverse video. The video and audio will be in sync automatically in the output file reversed.mkv, no need to worry about the input frame rate or anything else.
On one video if I only specified the -vf reverse to reverse video (but not audio), the output file didn't play correctly in mkv format but did work if I changed it to mp4 output format (I don't think this use case of reversing video only but not audio is common, but if you do run into this issue you can try changing the output format). On large input videos that exceed the RAM available in your computer, this method may not work and you may need to chop up the input file or use the old solution below.
Old Solution
One issue is the frame rate can vary depending on the video, many answers depend on a specific frame rate (like "-r 25" for 25 frames per second). If the frame rate in the video is different, this will cause the reversed audio and video to go out of sync.
You can of course manually adjust the frame rate each time (you can get the frame rate by running ffmpeg -i video.mkv and look for the number in front of the fps, this is sometimes a decimal number like 23.98). But with some bash code you can easily extract the fps, store it in a variable, and automatically pass it to the programs.
Based on this I've created the following bash script to do that. Simply chmod +x it and run it ./make-reversed-video.sh input.mkv output.mkv. The code is as follows:
#!/bin/bash
#Partially based on https://nhs.io/reverse/, but with some modifications, including automatic extraction of the frame rate.
#Get parameters.
VIDEO_FILE=$1
OUTPUT_FILE=$2
TEMP_FOLDER=$3
echo Using input file: $VIDEO_FILE
echo Using output file: $OUTPUT_FILE
mkdir /tmp/create_reversed_video
#Get frame rate.
FRAME_RATE=$(ffmpeg -i "$VIDEO_FILE" 2>&1 | grep -o -P '[0-9\\. ]+fps' | grep -o -P '[0-9\\.]+')
echo The frame rate is: $FRAME_RATE
#Extract audio from video.
ffmpeg -i "$VIDEO_FILE" -vn -ac 2 /tmp/create_reversed_video/audio.wav
#Reverse the audio.
sox -V /tmp/create_reversed_video/audio.wav /tmp/create_reversed_video/backwards.wav reverse
#Extract each video frame as an image.
ffmpeg -i "$VIDEO_FILE" -an -qscale 1 /tmp/create_reversed_video/%06d.jpg
#Recombine into reversed video.
ls -1 /tmp/create_reversed_video/*.jpg | sort -r | xargs cat | ffmpeg -framerate $FRAME_RATE -f image2pipe -i - -i /tmp/create_reversed_video/backwards.wav "$OUTPUT_FILE"
#Delete temporary files.
rm -rf /tmp/create_reversed_video
I've tested it and it works well on my Ubuntu 18.04 machine on lots of videos (after installing the dependencies like sox). Please let me know if it works on other Linux distributions and versions.
Related
I have an ffmpeg version built with VMAF library. I can use it to calculate the VMAF scores of a distorted video against a reference video using commands like this:
ffmpeg -i distorted.mp4 -i original.mp4 -filter_complex "[0:v]scale=640:480:flags=bicubic[main];[main][1:v]libvmaf=model_path=model/vmaf_v0.6.1.json:log_path=log.json" -f null -
Now, I remember there was a way to get VMAF scores while performing regular ffmpeg encoding. How can I do that at the same time?
I want to encode a video like this, while also calulate the VMAF of the output file:
ffmpeg -i original.mp4 -crf 27 -s 640x480 out.mp4
[edited]
Alright, scratch what I said earlier...
You should be able to use [the `tee` muxer](http://ffmpeg.org/ffmpeg-formats.html#tee-1) to save the file and pipe the encoded frames to another ffmpeg process. Something like this should work for you:
ffmpeg -i original.mp4 -crf 27 -s 640x480 -f tee "out.mp4 | [f=mp4]-" \
| ffmpeg -i - -i original.mp4 -filter_complex ...
(make them into 2 lines and remove \ for Windows)
Here is what works on my Windows PC (thanks to #Rotem for his help)
ffmpeg -i in.mp4 -vcodec libx264 -crf 27 -f nut pipe:
|
ffmpeg -i in.mp4 -f nut -i pipe:
-filter_complex "[0:v][1:v]libvmaf=log_fmt=json:log_path=log.json,nullsink"
-map 1 -c copy out.mp4
The main issue that #Rotem and I missed is that we need to terminate the libvmaf's output. Also, h264 raw format does not carry header info, and using `nut alleviates that issue.
There are a couple caveats:
testing with the testsrc example that #Rotem suggested in the comment below does not produce any libvmaf log, at least as far as I can see, but in debug mode, you can see the filter is getting initialized.
You'll likely see [nut # 0000026b123afb80] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8) message in the log. This just means that the frames are piped in faster than the 2nd ffmpeg is processing. FFmpeg does block on both ends, so no info should be lost.
For the full disclosure, I posted my Python test script on GitHub. It just runs the shell command, so it should be easy to follow even if you don't do Python.
I am using ffmpeg to read a rtmp stream, add a filter such as a blur box and create a different rtmp stream.
the command for example looks like:
ffmpeg -i <rtmp_source_url> -filter_complex "split=2[a][b];[a]crop=w=300:h=300:x=0:y=0[c];[c]boxblur=luma_radius=10:luma_power=1[blur];[b][blur]overlay=x=0:y=0[output]" -map [output] -acodec aac -vcodec libx264 -tune zerolatency -f flv <rtmp_output_url>
where rtmp_source_url is where the camera/drone is sending the flux and rtmp_output_url is the resuting video with the blur box.
the blur box need to move, either because the target moved or the camera did.
I want to do so without interrupting the output streaming.
I am using fluent-ffmpeg to create the ffmpeg process while a different part of the program compute where the blur box shall be.
thanks for you help and time!
Consider using a pipe to split up the processing.
See here - https://ffmpeg.org/ffmpeg-protocols.html#pipe
The accepted syntax is:
pipe:[number]
number is the number corresponding to the file descriptor of the pipe (e.g. 0 for stdin, 1 for stdout, 2 for stderr). If number is not specified, by default the stdout file descriptor will be used for writing, stdin for reading.
For example to read from stdin with ffmpeg:
cat test.wav | ffmpeg -i pipe:0
# ...this is the same as...
cat test.wav | ffmpeg -i pipe:
For writing to stdout with ffmpeg:
ffmpeg -i test.wav -f avi pipe:1 | cat > test.avi
# ...this is the same as...
ffmpeg -i test.wav -f avi pipe: | cat > test.avi
For example, you read a rtmp stream, add a filter such as a blur box and create a different rtmp stream. So, the first step is is to separate the incoming and outgoing stream -
ffmpeg -i <rtmp_source_url> -s 1920x1080 -f rawvideo pipe: | ffmpeg -s 1920x1080 -f rawvideo -y -i pipe: -filter_complex "split=2[a][b];[a]crop=w=300:h=300:x=0:y=0[c];[c]boxblur=luma_radius=10:luma_power=1[blur];[b][blur]overlay=x=0:y=0[output]"
-map [output] -acodec aac -vcodec libx264 -tune zerolatency -f flv <rtmp_output_url>
I do not know what criteria you have to vary the blur box, but now you can process the incoming frame in the second ffmpeg. Also, I used 1920x1080 as the video size - you can replace it with the actual size.
For the first iteration, do not worry about the audio, do your blur operation. As we are feeding rawvideo - in this example the audio will be ignored.
With FFmpeg you have the option -t which will set the duration of the output. However I do not see a way to limit the duration of the input. Take this command
ffmpeg -i video.mp4 -c copy -t 60 out.mp4
This simply creates a 60 second clip of the original video. However if I wanted to clip the audio while keeping the full video stream, FFmpeg does not seem to have an option for this.
I have tried simply clipping the audio first, then combining the clipped audio with the video file, but this causes video/audio sync issues for me.
‘-aframes number (output)’
Set the number of audio frames to record. This is an alias for -frames:a.
§ Audio Options
ffmpeg -i video.mp4 -c copy -aframes 100 out.mp4
Use the "-itsoffset" option.
This makes the first 10 seconds mute.
ffmpeg -i video.mp4 -vn -acodec copy -ss 10.0 out_audio.mp4
ffmpeg -itsoffset 10.0 -i out_audio.mp4 -i video.mp4 -vcodec copy -acodec copy out.mp4
I am trying to create a video out of a sequence of images and various audio files using FFmpeg. While it is no problem to create a video containing the sequence of images with the following command:
ffmpeg -f image2 -i image%d.jpg video.mpg
I haven't found a way yet to add audio files at specific points to the generated video.
Is it possible to do something like:
ffmpeg -f image2 -i image%d.jpg -i audio1.mp3 AT 10s -i audio2.mp3 AT 15s video.mpg
Any help is much appreciated!
EDIT:
The solution in my case was to use sox as suggested by blahdiblah in the answer below. You first have to create an empty audio file as a starting point like that:
sox -n -r 44100 -c 2 silence.wav trim 0.0 20.0
This generates a 20 sec empty WAV file. After that you can mix the empty file with other audio files.
sox -m silence.wav "|sox sound1.mp3 -p pad 0" "|sox sound2.mp3 -p pad 2" out.wav
The final audio file has a duration of 20 seconds and plays sound1.mp3 right at the beginning and sound2.mp3 after 2 seconds.
To combine the sequence of images with the audio file we can use FFmpeg.
ffmpeg -i video_%05d.png -i out.wav -r 25 out.mp4
See this question on adding a single audio input with some offset. The -itsoffset bug mentioned there is still open, but see users' comments for some cases in which it does work.
If it works in your case, that would be ideal:
ffmpeg -i in%d.jpg -itsoffset 10 -i audio1.mp3 -itsoffset 15 -i audio2.mp3 out.mpg
If not, you should be able to combine all the audio files with sox, overlaying or inserting silence to produce the correct offsets and then use that as input to FFmpeg. Not as convenient, but guaranteed to work.
One approach I can think of is to create your audio file for the whole duration of the video first and then mux the audio with the video file
I currently have a jpeg file which I converted to an flv using the following command:
ffmpeg -r 10 -b 180000 -i test.jpg test.mp4
Now, I want to increase the duration of this .mp4 clip, so the picture stays on the screen for more than a split second. Eventually, I hope to merge a stream of these files to create a slide show out of jpeg files.
Does anyone know how to increase the duration of a clip in ffmpeg?
Looping the input and setting a duration should achieve the effect you want:
ffmpeg -loop_input -i test.jpg -t 10 test.mp4
Doing something like this should work (at least for a single image):
ffmpeg -loop_input -i picture.jpg -r 1 -vcodec flv -b 192k -i Music.mp3 -acodec copy -shortest output.flv
I bet you could get it working with multiple images by adding more inputs though I haven't tested.
(http://forum.videohelp.com/threads/280695-FFMPEG-Loop-input-video)