When I use this command:
ffmpeg -i original.mp4 -codec:v:0 libx264 -b:v 650k -crf 21 -minrate:v 0k -maxrate:v 750k -bufsize:v 5000k -r 30 -preset slow -x264opts "no-scenecut" -vcodec libx264 -force_key_frames "expr:bitor(eq(t,0),gte(t,prev_forced_t+5))" -f mp4 test.mp4
I always get smaller file size than from this command (same command but without: -x264opts "no-scenecut"):
ffmpeg -i original.mp4 -codec:v:0 libx264 -b:v 650k -crf 21 -minrate:v 0k -maxrate:v 750k -bufsize:v 5000k -r 30 -preset slow -vcodec libx264 -force_key_frames "expr:bitor(eq(t,0),gte(t,prev_forced_t+5))" -f mp4 test.mp4
I thought that the scencut puts I frames only if it is more efficient to use I frame insted of P or B frame.
In what cases we need to use the scencut feature?
When a scenecut triggers it puts either an IDR if the distance is greater than min-keyint OR an I-frame otherwise.
Here's some pseudo-code posted on the doom9.org forum (adding it here for future reference):
encode current frame as (a really fast approximation of) a P-frame and an I-frame.
if ((distance from previous keyframe) > keyint) then
set IDR-frame
else if (1 - (bit size of P-frame) / (bit size of I-frame) < (scenecut / 100) * (distance from previous keyframe) / keyint) then
if ((distance from previous keyframe) >= minkeyint) then
set IDR-frame
else
set I-frame
else
set P-frame
encode frame for real.
You should use scenecut when you don't need a fixed GOP / forced keyframes. If you're trying to encode for ABR delivery then you can alternatively use two-pass encoding and generate a stat file for the highest resolution on pass-1 and then reuse it on pass-2 for each rendition.
Related
Currently I am using this...
ffmpeg -video_size 1920x1080 -framerate 1 -f x11grab -i :0.0+0,0 -f pulse -ac 2 -i default -t 00:00:10 Output.mkv
While ffmpeg is recording a video, I want it to significantly reduce both the size and quality compared to the ffmpeg command above.
In case you are curious, I am recording brief quality assurance videos to ensure a simple little web scraper I wrote in Python is scraping data properly (specifically, that it is clicking on a particular button, at a particular time, on a particular web page). My Python script triggers the command above to start recording my screen a few seconds before my Python script is supposed to click on that button.
Of course, to verify a button on a web page had been clicked on, low quality video resolution would normally suffice.
For libx264/libx265 the most important option to reduce both the size and quality is -crf. This option controls quality. A value of 51 provides the worst quality. If it's too terrible then use a lower number.
ffmpeg -video_size 1920x1080 -framerate 1 -f x11grab -i :0.0+0,0 -f pulse -channels 2 -i default -t 00:00:10 -c:v libx264 -crf 51 -c:a libopus Output.mkv
See FFmpeg Wiki: H.264.
For significantly reduce both the size and quality of Output.mkv you can use the next ffmpeg configuration:
crop: iw-(cut width in pixels):ih-(cut heigth in pixels)
scale: to set the ratio and resolution (example 1700x800)
crf: to set quality, where 0 is lossless, 23 is default, and 51 is worst possible. A lower value is a higher quality and a subjectively sane range is 18-28. Consider 18 to be visually lossless
bitrate value: -b:v value -minrate value and -maxrate max value (example -b:v 4000K -minrate 2000K -maxrate 6000K)
preset: in theory slow is best quality/size, and you can probe ultrafast
superfast
veryfast
faster
fast
medium – default preset
slow
slower
veryslow
Cut a part of video, changue the resolution, changue crf, and bitrate, first only video, then you can add audio in other work, dont mix, repeat, is very important, encoding/decoding audio and video separate, then you can mix all, but first the video like in this example
ffmpeg -i Output.mkv -map 0:v -vf crop=iw-150:ih-85,scale=ih*16/9:ih,scale=1072:732,setsar=1 -c:v libx264 -crf 17 -b:v 4000K -maxrate 6000K -bufsize 4M -movflags -faststart -preset veryfast -dn video-new.mkv
I used FFmpeg with this command to convert a video:
ffmpeg -i input -c:v libx264 -x264-params opencl=true -preset veryslow -crf 19 -maxrate 7000k -profile:v high -level 4.0 -bf 2 -coder 1 -pix_fmt yuv420p -c:a copy output.mkv
Note that I set -maxrate 7000k to set the maximum bit rate for the video. Still, the end result video has a maximum bit rate of 38.0 Mb/s.
Here are the results before (to the left) and after (to the right), if that helps.
Am I using maxrate properly? Should not the video be capped at 7000 kb/s?
maxrate is enforced via the bufsize option. No bufsize, no enforcement. See https://stackoverflow.com/a/33612662
The smaller the bufsize relative to maxrate, closer the actual peak bitrate to maxrate, but expect transient quality dips (if maxrate is too low for desired quality).
Start with
-maxrate 7000k -bufsize 7000k
I'm using already using the line below to transpose the source, but I'm facing a problem of the watermark being out of proportion when the video resolution is different
How can I make watermark fit on different video sizes?
ffmpeg -i input -i watermark.png -filter_complex "transpose=1,overlay=-40:300" -vb 370k -minrate 300k -maxrate 350k -bufsize 350k -aspect "720:1280" -s "360x640" -c:v libx264 -profile:v "Main" -level "3.1" -r 25 -g 25 -keyint_min 50 -x264opts "keyint=50:min-keyint=50:no-scenecut" -c:a aac -strict experimental -b:a 32000 -ar 32000 -ac 1 output
The scale2ref filter is meant for this use case.
-filter_complex "[0]transpose=1[v];[1][v]scale2ref=oh*mdar:ih/8[w][v];[v][w]overlay=X:Y"
The watermark's height will be resized to 1/8th the height of the video. The width will be proportionally resized.
I am using the following command to encode an AVI to an H264 video for use in an HTML5 video tag:
ffmpeg -y -i "test.avi" -vcodec libx264 -vpre slow -vpre baseline -g 30 "out.mp4"
And this works just fine. But I also want to create a placeholder video (long story) from a single still image, so I do this:
ffmpeg -y -i "test.jpg" -vcodec libx264 -vpre slow -vpre baseline -g 30 "out.mp4"
And this doesn't work. What gives?
EDIT: After trying LordNeckbeards answer, here is my full output: http://pastebin.com/axhKpkLx
Example for a 10 second output:
ffmpeg -loop 1 -framerate 24 -i input.jpg -c:v libx264 -preset slow -tune stillimage -crf 24 -vf format=yuv420p -t 10 -movflags +faststart output.mp4
Same thing but with audio. The output duration will match the input audio duration:
ffmpeg -loop 1 -framerate 24 -i input.jpg -i audio.mp3 -c:v libx264 -preset slow -tune stillimage -crf 24 -vf format=yuv420p -c:a aac -shortest -movflags +faststart output.mp4
-loop 1 loops the image input.
-framerate sets the frame rate of the image input. Default is 25. Some players have issues with low frame rates so a value over 6 or so is recommended.
-i input.jpg the input.
-c:v libx264 the H.264 video encoder.
-preset x264 encoding preset. Use the slowest one you can.
-tune x264 tuning for various adjustments to fit specific situations.
-crf for quality. A lower value results in higher quality. Use the highest value that still provides an acceptable quality to you. Default is 23.
-vf format=yuv420p outputs the pixel format as yuv420p. This ensures the output uses a widely acceptable chroma sub-sampling scheme. Recommended for libx264 when encoding from images.
-c:a aac the AAC audio encoder. If your input is already AAC or M4A then use -c:a copy instead to stream copy instead of re-encode.
-t 10 (in the first example) makes a 10 second output. Needed because the image is looping indefinitely.
-shortest (in the second example) makes the output the same duration as the shortest input. In this case it is the audio since the image is looping indefinitely.
-movflags +faststart relocates the moov atom to the beginning of the file after encoding is finished. Allows playback to begin faster in progressive download playing; otherwise the whole video must be downloaded before playing.
-profile:v main (optional) some devices can't handle High profile.
See FFmpeg Wiki: H.264 for more info.
I am using ffmpeg to convert the videos into mp4.Its working fine and its playing with high quality.No problem.But the worst case is I uploaded 14Mb file and after converting it goes to 30 Mb file.I am using the following the script to convert
exec("ffmpeg -i videowithaudio.flv -vcodec libx264 -vpre hq -vpre ipod640 -b 250k -bt 50k -acodec libfaac -ab 56k -ac 2 -s 480x320 video_out_file.mp4 > output1.txt 2> apperror1.txt"); //webkit compatible
I am using PHP for executing this command.Could you please help me how to reduce the file size from this 30Mb (nearly to uploaded file size is ok) with same quality.
Files converted from flv to mp4 will always have greater size than the source file. Generally flv files are smaller than other formats, thats why youtube converts all files to flv.
you can use -sameq parameter to retain the quality of video and lesser file size of resulting output file.
Example 1:
ffmpeg -i input.flv -sameq -ar 22050 output.mp4
Example 2:
exec("/usr/bin/ffmpeg -y -i input.flv -acodec libfaac -sameq -ar 44100 -ab 96k -coder ac -me_range 16 -subq 5 -sc_threshold 40 -b 1600k -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 -i_qfactor 0.71 -keyint_min 25 -b_strategy 1 -g 250 -r 20 output.mp4");
I created this command by searching alot and this fulfills my requirements, using this you can get a bit less file size but with same quality.
Hope this works for you also.
You should try playing around with your key frames rate (-g). Frames between key frames have only the pixels different from the previous key frame. If your key frames are too far apart, all pixels are present in middle frames (increasing size), too close and the number of key frames increases the file size.
Note that the optimal key frame rate will be different for each video, so you need to find a middle ground.
exec("ffmpeg -i videowithaudio.flv -vcodec libx264 -vpre hq -vpre ipod640 -b 250k -bt 50k -acodec libfaac -ab 56k -ac 2 -s 480x320 video_out_file.mp4 > output1.txt 2> apperror1.txt"); //webkit compatible
Important for the filesize, is the bitrate. The bitrate specifies how many bytes to use per second video. If you decrease the bitrate, the filesize will also become smaller.
You are currently using 250kbit/s video (-b 250k) and 56kbit/s audio (-ab 56k), so you have to decrease those numbers. For example you can try :-b 100k -ab 32k. But keep in mind that the quality will also decrease when you decrease the bitrate. If the quality becomes too bad, you can also decrease the framerate or frame size to increase the quality.