I'm using FFMPEG to capture a live stream from a directshow device (here a VGA2USB adapter).
I need to generate snapshot on scene change which I manage to do with the following command line :
ffmpeg -v verbose -r 20 -f dshow -rtbufsize 2000M -i "video=VGA2USB V2U115452" -s 1024x768 -pix_fmt yuv420p -filter:v yadif=2:0:0 -vcodec mjpeg -muxdelay 0.1 -f image2 -vf select='gt(scene\,0.1)' -vsync vfr "c:\tmp\image%3d.jpg"
This command line generates the snapshot but they are "delayed". I mean, when a scene change is detected with the filter, the previous snapshot is written in the jpg file and the current stay in "buffer" (or whereever it is).
If I try to generate a snapshot every 5 seconds (with -vf fps=fps=1/5 option) the first snapshot is written on the hard disk at the 5th second.
How can I force FFMPEG to write immediately the snapshot and not to wait the next snapshot ?
Thanks for any help you can provide.
Related
Before posting I have searched and found similar questions on stackoverflow (I list some below) - none have helped me towards a solution, hence this post. The duration that each image is shown within the movie file differs from many posts that I have seen thus far.
A camera captures 1 image every 30 seconds. I need stream them, preferably via HLS, thus I wrap 2 images in an MP4. I then convert MP4 to mpegts. Each MP4 and TS file play fine individually (each contain two images, each image transitions after 30seconds, each movie file is 1minute long).
When I reference the two TS files in an M3U8 playlist, only the first TS file gets played. Can anyone advise why it stops and how I can get it to play all the TS files that I expect to create, not just the first TS file? Besides my ffmpeg commands, I also include my VLC log file (though I expect to stream to Firefox/Chrome clients). I am using ffmpeg 4.2.2-static installed on an AWS EC2 with AMI2 Linux.
I have four jpgs named image11.jpg, image12.jpg, image21.jpg, image22.jpg - The images look near identical as only the timestamp in top left changes.
The following command creates 1.mp4, using image11.jpg and image12.jpg, each image displayed for 30 seconds, total duration of the mp4 is 1 minute. It plays like expected.
ffmpeg -y -framerate 1/30 -f image2 -i image1%1d.jpg -c:v libx264 -vf "fps=1,format=yuvj420p" 1.mp4
I then convert 1.mp4 to an mpegts file, creating 1.ts. It plays like expected.
ffmpeg -y -i 1.mp4 -c:v libx264 -vbsf h264_mp4toannexb -flags -global_header -f mpegts 1.ts
I repeat the above steps except specific to image21.jpg and image22.jpg, creating 2.mp4 and 2.ts
ffmpeg -y -framerate 1/30 -f image2 -i image1%1d.jpg -c:v libx264 -vf "fps=1,format=yuvj420p" 2.mp4
ffmpeg -y -i 1.mp4 -c:v libx264 -vbsf h264_mp4toannexb -flags -global_header -f mpegts 2.ts
Thus now I have 1.mp4, 1.ts, 2.mp4, 2.ts and all four play individually just fine.
Using ffprobe I can confirm their duration is 60seconds, for example:
ffprobe -i 1.ts -v quiet -show_entries format=duration -hide_banner -print_format json
My m3u8 playlist follows:
#EXTM3U
#EXT-X-VERSION:4
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-MEDIA-SEQUENCE:1
#EXT-X-TARGETDURATION:60.000
#EXTINF:60.0000,
1.ts
#EXTINF:60.000,
2.ts
#EXT-X-ENDLIST
Can anyone advise where I am going wrong?
VLC Error Log (though I expect to play via web browser)
I have researched the process using these (and other pages) as a guide:
How to create a video from images with ffmpeg
convert from jpg to mp4 by ffmpeg
ffmpeg examples page
FFMPEG An Intermediate Guide/image sequence
How to use FFmpeg to convert images to video
Take a look at the start_pts/start_time in the ffprobe -show_streams output, my guess is that they all start at zero/near-zero which will cause playback to fail after your first segment.
You can still produce them independently but you will want to use something like -output_ts_offset to correctly set the timestamps for subsequent segments.
The following solution works well for me. I have tested it uninterrupted for more than two hours and believe it ticks all my boxes. (Edited because I forgot the all important -re tag)
ffmpeg will loop continuously, reading test.jpg and stream it to my RTMP server. When my camera posts an image every 30seconds, I copy the new image on top of the existing test.jpg which in effect changes what is streamed out.
Note the command below is all one line, I have put new lines in to assist reading and The order of the parameters are important - the loop and fflags genpts for example must appear before the -i parameter
ffmpeg
-re
-loop 1
-fflags +genpts
-framerate 1/30
-i test.jpg
-c:v libx264
-vf fps=25
-pix_fmt yuvj420p
-crf 30
-f fifo -attempt_recovery 1 -recovery_wait_time 1
-f flv rtmp://localhost:5555/video/test
Some arguments explained:
-re implies play in real time
loop 1 (1 turns the loop on, 0 off)
-fflags +genpts is something I only half understand. PTS I believe is the start/end time of the segment and without this flag, the PTS is reset to zero with every new image. Using this arguement means I avoid EXT-X-DISCONTINUITY when a new image is served.
-framerate 1/30 means one frame for 30seconds
-i test.jpg is my image 'placeholder'. As new images are received via a separate script, it overwrites this image. When combined with loop it means the ffmpeg output will reference the new image.
-c:v libx264 is for H264 video output formating
-vf fps=25 Removing this, or using a different value resulted in my output stream not being 30seconds.
-pix_fmt yuvj420p (sometimes I have seen yuv420p referenced but this did not work on my environment). I believe there are different jpg colour palettes and this switch ensures I can process a wider choice.
-crf 30 implies highest quality image, lowest compression (important for my client)
-f fifo -attempt_recovery 1 -recovery_wait_time 1 -f flv rtmp://localhost:5555/video/test is part of the magic to go with loop. I believe it keeps the connection open with my stream server, reduces the risk of DISCONTINUITY in the play list.
I hope this helps someone going forward.
The following links helped nudge me forward and I share as it might help others to improve upon my solution
Creating a video from a single image for a specific duration in ffmpeg
How can I loop one frame with ffmpeg? All the other frames should point to the first with no changes, maybe like a recusion
Display images on video at specific framerate with loop using FFmpeg
Loop image ffmpeg HLS
https://trac.ffmpeg.org/wiki/Slideshow
https://superuser.com/questions/1699893/generate-ts-stream-from-image-file
https://ffmpeg.org/ffmpeg-formats.html#Examples-3
https://trac.ffmpeg.org/wiki/StreamingGuide
Machine learning algorithms for video processing typically work on frames (images) rather than video.
In my work, I use ffmpeg to dump a specific scene as a sequence of .png files, process them in some way (denoise, deblur, colorize, annotate, inpainting, etc), output the results into an equal number of .png files, and then update the original video with the new frames.
This works well with constant frame-rate (CFR) video. I dump the images as so (eg, 50-frame sequence starting at 1:47):
ffmpeg -i input.mp4 -vf "select='gte(t,107)*lt(selected_n,50)'" -vsync passthrough '107+%06d.png'
And then after editing the images, I replace the originals as so (for a 12.5fps CFR video):
ffmpeg -i input.mp4 -itsoffset 107 -framerate 25/2 -i '107+%06d.png' -filter_complex "[0]overlay=eof_action=pass" -vsync passthrough -c:a copy output.mp4
However, many of the videos I work with are variable frame-rate (VFR), and this has created some challenges.
A simple solution is to convert VFR video to CFR, which ffmpeg wants to do anyway, but I'm wondering if it's possible to avoid this. The reason is that CFR requires either dropping frames - since the purpose of ML video processing is usually to improve the output, I'd like to avoid this - or duplicating frames - but an upscaling algorithm that I'm working with right now uses the previous and next frame for data - if the previous or next frame is a duplicate, then ... no data for upscaling.
With -vsync passthrough, I had hoped that I could simply remove the -framerate option, and preserve the original frames as-is, but the resulting command:
ffmpeg -i input.mp4 -itsoffset 107 -i '107+%06d.png' -filter_complex "[0]overlay=eof_action=pass" -vsync passthrough -c:a copy output.mp4
uses ffmpeg's default of 25fps, and drops a lot of frames. Is there a reliable way to replace frames in VFR video?
Yes, it can be done, but it's complicated. It is crucial that the overlay video have exactly the same frame timestamps as the underlay video for this process to work reliably. Generating such a VFR video segment overlay requires capturing the frame timestamps from the source video to generate a precisely timed replacement segment.
The short version of the process is to replace the above commands with the following to extract the images:
ffmpeg -i input.mp4 -vf "select='gte(t,107)*lt(selected_n,50)',showinfo" -vsync passthrough '107+%06d.png' 2>&1 | 'sed s/\r/\n/g' | showinfo2concat.py --prefix="107+" >concat.txt
This requires a script that can be downloaded here. After editing the images, update the source video with:
ffmpeg -i input.mp4 -f concat -safe 0 -i concat.txt -filter_complex"[1]settb=1/90000,setpts=9644455+PTS*25/90000[o];[0:v:0][o]overlay=eof_action=pass" -vsync passthrough -r 90000 output.mp4
Where 90000 is the timescale (inverse of timebase), and 9644455 is the PTS of the first frame to replace.
See the source for more details about what these commands actually do.
Im using ffmpeg to change resolution of video file and after conversion to another location the video lasts 0 seconds, but originally it lasts 2mins
My ffmepg code:
ffmpeg -i input.mp4 -filter:v scale=480:320 -t 5 output.mp4
Why are you using the -t modifier? You want to cut the video up? Otherwise, this will convert the whole length to the new quality.
ffmpeg -i input.mp4 -filter:v scale480:320 output.mp4
I'm capturing video from 4 cameras connected with HDMI through a capture card. I'm using ffmpeg to save the video feed from the cameras to multiples jpeg files (30 jpeg per second per camera).
I want to be able to save the images with the capture time. Currently I'm using this command for one camera:
ffmpeg -f video4linux2 -pixel_format yuv420p -timestamps abs -I /dev/video0 -c:a jpeg -t 60 -ts_from_file 2 camera0-%5d.jpeg
It saves my file with the names camera0-00001.jpg, camera0-00002.jpg, etc.
Then I rename my file with camera0-HH-mm-ss-(1-30).jpeg based on the modified time of the file.
So in the end I have 4 files with the same time and same frame like this:
camera0-12-00-00-1.jpeg
camera1-12-00-00-1.jpeg
camera2-12-00-00-1.jpeg
camera3-12-00-00-1.jpeg
My issue is that the file may be offset from one to two frame. They may have the same name but sometime one or two camera may show different frame.
Is there a way to be sure that the capture frames has the actual time of the capture and not the time of the creation of the file?
You can use the mkvtimestamp_v2 muxer
ffmpeg -f video4linux2 -pixel_format yuv420p -timestamps abs -copyts -i /dev/video0 \
-vf setpts=PTS-STARTPTS -vsync 0 -vframes 1800 camera0-%5d.jpeg \
-c copy -vsync 0 -vframes 1800 -f mkvtimestamp_v2 timings.txt
timings.txt will have output like this
# timecode format v2
1521177189530
1521177189630
1521177189700
1521177189770
1521177189820
1521177189870
1521177189920
1521177189970
...
where each reading is the Unix epoch time in milliseconds.
I've switched to output frame count limit to stop the process instead of -t 60. You can use -t 60 for the first output since we are resetting timestamps there, but not for the second. If you do that, remember to only use the first N entries from the text file, where N is the number of images produced.
trying to get my head around ffmpeg to create a slideshow where each image is displayed for ~5 seconds with some audio. created a bat file to run the following so far:
ffmpeg -f image2 -i image-%%03d.jpg -i music.mp3 output.mpg
It gets the images and displayes them all very fast in the first second of the video, it then plays out the rest of the audio while showing the last image.
I want to make the images stay up longer (about 5 seconds), and stop the video after the last frame (not playing the rest of the song), are either of these things possible? i could hack the frame rate thing i guess by having hundreds of the same image in order to keep it up longer, but this is far from ideal!
Thanks
The default encoder for mpg output, mpeg1video, is strict about the allowed frame rates, so an input and an output -r are required:
ffmpeg -r 1/5 -i image-%03d.jpg -i music.mp3 -r 25 -qscale:v 2 -shortest -codec:a copy output.mpg
The input images will have a frame rate of 1 frame every 5 seconds and the output will duplicate frames to reach 25 frames per second.
-f image2 is generally not required.
-qscale:v can control output quality. A sane range is 2-5.
-shortest will make the output duration the same as the shortest input duration.
-codec:a copy copy your MP3 audio instead of re-encoding.
MPEG-1 video has more modern alternatives. See the FFmpeg and x264 Encoding Guide for more info.
Also see:
* FFmpeg FAQ: How do I encode single pictures into movies?
* FFmpeg Wiki: Create a video slideshow from images
You could use the filter fps instead of output framerate
ffmpeg -r 1/5 -i img%03d.png -i musicfile -c:v libx264 -vf fps=25 -pix_fmt yuv420p out.mp4
This however skips the last image for me strangely.