digital_video_introduction/README.md

Introduction

Please make sure you run ./setup.sh first.

General commands

Inspect stream

To see some details:

./s/mediainfo /files/v/small_bunny_1080p_30fps.mp4

To see full details:

./s/mediainfo --Details=1 /files/v/small_bunny_1080p_30fps.mp4

To see only the frame, slice types:

./s/mediainfo --Details=1 /files/v/small_bunny_1080p_30fps.mp4 | grep slice_type

Transmuxing

From mp4 to ts:

./s/ffmpeg -i /files/v/small_bunny_1080p_30fps.mp4  /files/v/small_bunny_1080p_30fps.ts

From mp4 to ts explicitly telling to copy audio and video codec:

./s/ffmpeg -i /files/v/small_bunny_1080p_30fps.mp4 -c:a copy -c:v copy  /files/v/small_bunny_1080p_30fps.ts

Transcoding

From h264 to vp9:

./s/ffmpeg -i /files/v/small_bunny_1080p_30fps.mp4 -c:v libvpx-vp9 -c:a libvorbis /files/v/small_bunny_1080p_30fps_vp9.webm

From h264 to h265:

./s/ffmpeg -i /files/v/small_bunny_1080p_30fps.mp4 -c:v libx265 /files/v/small_bunny_1080p_30fps_h265.mp4

From h264 to h264 with I-frame at each second (for a 30FPS video):

./s/ffmpeg -i /files/v/small_bunny_1080p_30fps.mp4 -c:v libx264 -x264-params keyint=30:min-keyint=30:no-scenecut=1 -c:a copy /files/v/small_bunny_1080p_30fps_h264_keyframe_each_second.mp4

Count how many I-slice (keyframes) were inserted:

./s/mediainfo --Details=1 /files/v/small_bunny_1080p_30fps_h264_keyframe_each_second.mp4 | grep "slice_type I" | wc -l

Transrating

CBR from 1928 kbps to 964 kbps:

./s/ffmpeg -i /files/v/small_bunny_1080p_30fps.mp4 -b:v 964K -minrate 964K -maxrate 964K -bufsize 2000K  /files/v/small_bunny_1080p_30fps_transrating_964.mp4

Constrained VBR or ABR from 1928 kbps to max=3856 kbps ,min=964 kbps:

./s/ffmpeg -i /files/v/small_bunny_1080p_30fps.mp4 -minrate 964K -maxrate 3856K -bufsize 2000K  /files/v/small_bunny_1080p_30fps_transrating_964_3856.mp4

Transsizing

From 1080p to 480p:

./s/ffmpeg -i /files/v/small_bunny_1080p_30fps.mp4 -vf scale=480:-1 /files/v/small_bunny_1080p_30fps_transsizing_480.mp4

Adaptive bitrate streaming

HLS streaming:

A VOD stream with 1s chunk size

./s/ffmpeg -i /files/v/small_bunny_1080p_30fps_h264_keyframe_each_second.mp4 -c:a copy -c:v libx264 -x264-params keyint=30:min-keyint=30:no-scenecut=1 -hls_playlist_type vod -hls_time 1 /files/v/playlist_keyframe_each_second.m3u8

Playlists for 720p(2628kbs), 480p(480p1128kbs) and 240p(264kbs) streams

./s/ffmpeg -i /files/v/small_bunny_1080p_30fps_h264_keyframe_each_second.mp4 \
             -c:a copy -c:v libx264 -x264-params keyint=30:min-keyint=30:no-scenecut=1 \
             -b:v 2500k -s 1280x720 -profile:v high -hls_time 1 -hls_playlist_type vod /files/v/720p2628kbs.m3u8 \
             -c:a copy -c:v libx264 -x264-params keyint=30:min-keyint=30:no-scenecut=1 \
             -b:v 1000k -s 854x480 -profile:v high -hls_time 1 -hls_playlist_type vod /files/v/480p1128kbs.m3u8 \
             -c:a copy -c:v libx264 -x264-params keyint=30:min-keyint=30:no-scenecut=1 \
             -b:v 200k -s 426x240 -profile:v high -hls_time 1 -hls_playlist_type vod /files/v/240p264kbs.m3u8

The variant playlist

cat <<EOF > v/variant.m3u8
#EXTM3U
#EXT-X-VERSION:6
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=2500000,CODECS="avc1.640028,mp4a.40.2",RESOLUTION=1280x720
720p2628kbs.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=1000000,CODECS="avc1.4d001f,mp4a.40.2",RESOLUTION=854x480
480p1128kbs.m3u8
#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=200000,CODECS="avc1.42001f,mp4a.40.2",RESOLUTION=426x240
240p264kbs.m3u8
EOF

Video quality perception

You can learn more about vmaf and general video quality perception.

# generating a 2 seconds example video
./s/ffmpeg -y -i /files/v/bunny_1080p_30fps.mp4 -ss 00:01:24 -t 00:00:02  /files/v/smallest_bunny_1080p_30fps.mp4

# generate a transcoded video (600kbps vp9)
./s/ffmpeg -i /files/v/smallest_bunny_1080p_30fps.mp4 -c:v libvpx-vp9 -b:v 600K -c:a libvorbis /files/v/smallest_bunny_1080p_30fps_vp9.webm

# extract the yuv (yuv420p) color space from them
./s/ffmpeg -i /files/v/smallest_bunny_1080p_30fps.mp4 -c:v rawvideo -pix_fmt yuv420p /files/v/smallest_bunny_1080p_30fps.yuv
./s/ffmpeg -i /files/v/smallest_bunny_1080p_30fps_vp9.webm -c:v rawvideo -pix_fmt yuv420p /files/v/smallest_bunny_1080p_30fps_vp9.yuv

# run vmaf original h264 vs transcoded vp9
./s/vmaf run_vmaf yuv420p 1080 720 /files/v/smallest_bunny_1080p_30fps.yuv /files/v/smallest_bunny_1080p_30fps_vp9.yuv --out-fmt json