adds instructions for ffmpeg examples

README.md

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+# Introduction
+
+Please make sure you run `./setup.sh` first.
+
+# General commands
+
+To see some details:
+
+```
+./s/mediainfo.sh /files/v/small_bunny_1080p_30fps.mp4
+```
+
+To see full details:
+
+```
+./s/mediainfo.sh --Details=1 /files/v/small_bunny_1080p_30fps.mp4
+```
+
+To see only the frame, slice types:
+
+```
+./s/mediainfo.sh --Details=1 /files/v/small_bunny_1080p_30fps.mp4 | grep slice_type
+```
+
+Transmuxing `mp4` to `ts`:
+
+```
+./s/ffmpeg.sh -i /files/v/small_bunny_1080p_30fps.mp4  /files/v/small_bunny_1080p_30fps.ts
+```
+
+Transmuxing `mp4` to `ts` explicitly telling to copy audio and video codec:
+
+```
+./s/ffmpeg.sh -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.sh -i /files/v/small_bunny_1080p_30fps.mp4 -c:v libvpx-vp9 -c:a libvorbis /files/v/small_bunny_1080p_30fps_vp9.mp4
+```
+
+Transcoding from `h264` to `h265`:
+
+```
+./s/ffmpeg.sh -i /files/v/small_bunny_1080p_30fps.mp4 -c:v libx265 /files/v/small_bunny_1080p_30fps_h265.mp4
+```
+
+Transcoding from `h264` to `h264` with I-frame at each second (for a 30FPS video):
+
+```
+./s/ffmpeg.sh -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.sh --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.sh -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
+```
+
+Transrating (Constrained VBR or ABR) from `1928 kbps` to `max=3856 kbps ,min=964 kbps`:
+
+```
+./s/ffmpeg.sh -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.sh -i /files/v/small_bunny_1080p_30fps.mp4 -vf scale=480:-1 /files/v/small_bunny_1080p_30fps_transsizing_480.mp4
+```
+
+Generate adaptive bitrate streaming HLS:
+
+```
+# a vod with 1s chunk size
+./s/ffmpeg.sh -i /files/v/small_bunny_1080p_30fps_h264_keyframe_each_second.mp4 -hls_playlist_type vod -hls_time 1 /files/v/playlist.m3u8
+
+# remember that you're in fact transcoding too, now a vod with 1s chunk size
+./s/ffmpeg.sh -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
+
+# creating playlists for 720p(2628kbs), 480p(480p1128kbs) and 240p(264kbs) streams.
+./s/ffmpeg.sh -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
+
+# create 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
+
+```