I used to change the bitrate of audio files by using
ffmpeg -i input.mp3 -ab 96k output.mp3
and it works perfectly. Now I want to pass the output as pipe in Ffmpeg and perform some other task. I have took the reference of this documentation and modified the above ffmpeg command into
ffmpeg -i input.mp3 -ab 96k pipe:1 | aws s3 cp - s3://mybucket/output.mp3
But this doesn't work.
Only if i use pipe as below then it works.
ffmpeg -i input.mp3 -f mp3 pipe:1 | aws s3 cp - s3://mybucket/output.mp3
But this doesn't change the bitrate of the audio. Can anyone please help me how can I achieve my target of changing the bitrate and passing the output as Pipe
You have to specify the output format manually. When outputting to file, ffmpeg guesses format based on extension, which can't be done when piping.
Use
ffmpeg -i input.mp3 -ab 96k -f mp3 pipe:1 | aws s3 cp - s3://mybucket/output.mp3
Related
I want to capture video+audio from directshow device like webcam and stream it to RTMP server. This part no problem. But the problem is that I want to be able to see the preview of it. After a lot of search someone said pipe the input using tee muxer to ffplay. but I couldn't make it work. Here is my code for streaming to rtmp server. how should I change it?
ffmpeg -rtbufsize 8196k -framerate 25 -f dshow -i video="Microsoft® LifeCam Studio(TM)":audio="Desktop Microphone (Microsoft® LifeCam Studio(TM))" -vcodec libx264 -acodec aac -strict -2 -b:v 1024k -b:a 128k -ar 48000 -s 720x576 -f flv "rtmp://ip-address-of-my-server/live/out"
Here is the final code I used and it works.
ffmpeg -rtbufsize 8196k -framerate 25 -f dshow -i video="Microsoft® LifeCam Studio(TM)":audio="Desktop Microphone (Microsoft® LifeCam Studio(TM))" -vcodec libx264 -acodec aac -strict -2 -f tee -map 0:v -map 0:a "[f=flv]rtmp://ip-address-and-path|[f=nut]pipe:" | ffplay pipe:
The core command for those running ffmpeg on a Unix-compatible system (e.g. MacOS, BSD and GNU-Linux) is really quite simple. It's to redirect or to "pipe" one of the outputs of ffmpeg to ffplay. The main problem here is that ffmpeg cannot autodetect the media format (or container) if the output doesn't have a recognizable file extension such as .avi or .mkv.
Therefore you should specify the format with the option -f. You can list the available choices for option -f with the ffmpeg -formats command.
In the following GNU/Linux command example, we record from an input source named /dev/video0 (possibly a webcam). The input source can also be a regular file.
ffmpeg -i /dev/video0 -f matroska - filename.mkv | ffplay -i -
A less ambiguous way of writing this for non-Unix users would be to use the special output specifier pipe.
ffmpeg -i /dev/video0 -f matroska pipe:1 filename.mkv | ffplay -i pipe:0
The above commands should be enough to produce a preview. But to make sure that you get the video and audio quality you want, you also need to specify, among other things, the audio and video codecs.
ffmpeg -i /dev/video -c:v copy -c:a copy -f matroska - filename.mkv | ffplay -i -
If you choose a slow codec like Google's AV1, you'd still get a preview, but one that stutters.
Im using this ffmpeg command to convert mp3 to wav:
ffmpeg -i audio.mp3 -acodec libmp3lame -ab 64k -ar 16000 audio.wav
and this command to create waveform from audio.wav:
wav2png --foreground-color=ffb400aa --background-color=2e4562ff -o example4.png papa2.wav
I would love to know, how to run this commands multiple? For example, when conversion from .mp3 to .wav is done, then run the wav2png command.
Thank You!
You have several options here:
Option 1: Use &&
In Bash you can use an and list to concatenate commands. Each command will be executed one after the other. The and list will terminate when a command fails, or when all commands have been successfully executed.
ffmpeg -i audio.mp3 audio.wav && wav2png -o output.png audio.wav
Using -acodec libmp3lame when outputting to WAV makes no sense, so I removed that.
WAV ignores bitrate options, so I removed -ab.
Do you really need to change the audio rate (-ar)? Removed.
Option 2: Pipe from ffmpeg to wav2png
Instead of making a temporary WAV file you can pipe the output from ffmpeg directly to wav2png:
ffmpeg -i audio.mp3 -f wav - | wav2png -o output.png /dev/stdin
Option 3: Just use ffmpeg
Saving the best for last, you can try the showwavespic filter.
ffmpeg -i music.wav -filter_complex showwavespic=s=640x320 showwaves.png
If you want to make a video of the wave form, then try showwaves.
You can see a colored example at Generating a waveform using ffmpeg.
I'm trying to convert a gif file to webm file using the below which works fine however I’m wondering is it also possible to reverse it as well using ffmpeg or would I need to reverse it using imagemagick first then cover it using ffmpeg
ffmpeg -i your_gif.gif -c:v libvpx -crf 12 -b:v 500K output.webm
Any help is appreciated
The script posted here might help you.
This one seems to be in bash but ripping the commands should work on Windows as well.
https://github.com/WhatIsThisImNotGoodWithComputers/ffmpeg-webm-scripts
These are the relevant lines of code (note that they need to edited for your setup):
ffmpeg -i "${INPUT_FILE}" -ss $START_TIME -to $TO_TIME -an -qscale 1 $TEMP_FOLDER/%06d.jpg
cat $(ls -r $TEMP_FOLDER/*jpg) | ffmpeg -f image2pipe -vcodec mjpeg -r 25 -i - -c:v libvpx -crf 20 -b:v $FRAMERATE $CROPSCALE -threads 0 -an $OUTPUT_FILE
You basically have to convert all stills to jpgs and then back into webm, but in reverse order.
From ffmpeg --help, you can see what codecs ffmpeg supports with ffmpeg -codecs. ffmpeg -codecs|grep -i gif on mine says it supports gif.
ffmpeg checks extensions to get file type if you don't override,
ffmpeg -i onoz.webm onoz.gif
does the trick just fine.
I am using FFMPEG to convert uploaded videos to .flv, after conversion the flv video doesn't have information about it's duration. So the user cannot rewind/forward, replay or see a specific part of it. The code is as follows:
"ffmpeg -i $srcfile_path -s 320x240 -ar 44100 -b 2048k -r 12 $desfilepath";
Please help. Thanks in advance.
I ran the following command and it worked.
"ffmpeg -i $srcfile_path -f flv - | flvtool2 -U stdin $desfilepath"
This requires flvtool installed on your system. I am using an FFMPEG and FLVTOOL2 enabled server, so it worked.
That's very strange, I have been using ffmpeg to convert videos from one format to another without any issues. See example below:
ffmpeg -i input.avi -b:a 192K -b:v 2400 -s hd720 -c:v mpeg2video output.mpg
I am sure you know the syntax.
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.