| description | While working with audio/video we usually do a set of tasks with the media. |
|---|
What? the act of converting one of the streams (audio or video) from one CODEC to another one.
Why? sometimes some devices (TVs, smartphones, console and etc) doesn't support X but Y and newer CODECs provide better compression rate.
How? converting an H264 (AVC) video to an H265 (HEVC).
$ ffmpeg \
-i bunny_1080p_60fps.mp4 \
-c:v libx265 \
bunny_1080p_60fps_h265.mp4
What? the act of converting from one format (container) to another one.
Why? sometimes some devices (TVs, smartphones, console and etc) doesn't support X but Y and sometimes newer containers provide modern required features.
How? converting a mp4 to a webm.
$ ffmpeg \
-i bunny_1080p_60fps.mp4 \
-c copy \ # just saying to ffmpeg to skip encoding
bunny_1080p_60fps.webm
What? the act of changing the bit rate, or producing other renditions.
Why? people will try to watch your video in a 2G (edge) connection using a less powerful smartphone or in a fiber Internet connection on their 4K TVs therefore you should offer more than on rendition of the same video with different bit rate.
How? producing a rendition with bit rate between 3856K and 2000K.
$ ffmpeg \
-i bunny_1080p_60fps.mp4 \
-minrate 964K -maxrate 3856K -bufsize 2000K \
bunny_1080p_60fps_transrating_964_3856.mp4Usually we'll be using transrating with transsizing. Werner Robitza wrote another must read/execute series of posts about FFmpeg rate control.
What? the act of converting from one resolution to another one. As said before transsizing is often used with transrating.
Why? reasons are about the same as for the transrating.
How? converting a 1080p to a 480p resolution.
$ ffmpeg \
-i bunny_1080p_60fps.mp4 \
-vf scale=480:-1 \
bunny_1080p_60fps_transsizing_480.mp4
What? the act of producing many resolutions (bit rates) and split the media into chunks and serve them via http.
Why? to provide a flexible media that can be watched on a low end smartphone or on a 4K TV, it's also easy to scale and deploy but it can add latency.
How? creating an adaptive WebM using DASH.
# video streams
$ ffmpeg -i bunny_1080p_60fps.mp4 -c:v libvpx-vp9 -s 160x90 -b:v 250k -keyint_min 150 -g 150 -an -f webm -dash 1 video_160x90_250k.webm
$ ffmpeg -i bunny_1080p_60fps.mp4 -c:v libvpx-vp9 -s 320x180 -b:v 500k -keyint_min 150 -g 150 -an -f webm -dash 1 video_320x180_500k.webm
$ ffmpeg -i bunny_1080p_60fps.mp4 -c:v libvpx-vp9 -s 640x360 -b:v 750k -keyint_min 150 -g 150 -an -f webm -dash 1 video_640x360_750k.webm
$ ffmpeg -i bunny_1080p_60fps.mp4 -c:v libvpx-vp9 -s 640x360 -b:v 1000k -keyint_min 150 -g 150 -an -f webm -dash 1 video_640x360_1000k.webm
$ ffmpeg -i bunny_1080p_60fps.mp4 -c:v libvpx-vp9 -s 1280x720 -b:v 1500k -keyint_min 150 -g 150 -an -f webm -dash 1 video_1280x720_1500k.webm
# audio streams
$ ffmpeg -i bunny_1080p_60fps.mp4 -c:a libvorbis -b:a 128k -vn -f webm -dash 1 audio_128k.webm
# the DASH manifest
$ ffmpeg \
-f webm_dash_manifest -i video_160x90_250k.webm \
-f webm_dash_manifest -i video_320x180_500k.webm \
-f webm_dash_manifest -i video_640x360_750k.webm \
-f webm_dash_manifest -i video_640x360_1000k.webm \
-f webm_dash_manifest -i video_1280x720_500k.webm \
-f webm_dash_manifest -i audio_128k.webm \
-c copy -map 0 -map 1 -map 2 -map 3 -map 4 -map 5 \
-f webm_dash_manifest \
-adaptation_sets "id=0,streams=0,1,2,3,4 id=1,streams=5" \
manifest.mpdPS: I stole this example from the Instructions to playback Adaptive WebM using DASH
There are many and many other usages for FFmpeg. I use it in conjunction with iMovie to produce/edit some videos for YouTube and you can certainly use it professionally.