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Podcasts von MP3 und Vorbis in OPUS transkodieren

Podcasts werden derzeit häufig im MP3-Format in Stereo mit 128-192 kbit/s ausgeliefert (etwas seltener findet man auch das datensparsamere OGG/Vorbis Format).

Bei Podcasts kann(!) jedoch ein datensparsameres Mono-Signal ausreichen

• und Opus ist (als Nachfolger von OGG/Vorbis) zur Zeit der effizienteste Codec in Bezug die

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OPML

OPML of podcasts. Often updates.

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Stefan's Podcast List #1

Some random podcasts ... In some random order ...

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Politk & Gesellschaft

Ganz offen gesagt

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ffmpeg -re -i INPUT -acodec libmp3lame -ab 160k -ar 44100 -f rtp rtp://host:port

#list device audio & video inputs
ffmpeg -f avfoundation -list_devices true -i ""

#stream from device audio & video inputs to rtmp
ffmpeg -f avfoundation -framerate 30 -i "0:2" -vcodec libx264 -tune zerolatency -s 1440x900 -acodec libmp3lame -f flv -strict -1 rtmp://host:port

#stream from audio inputs ONLY to rtmp
ffmpeg -f avfoundation -framerate 30 -i ":2" -acodec libmp3lame -f flv -strict -1 rtmp://host:port/live/$stream_name

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PERSONAL COMMAND LINE

FFMPEG :

Single source

ffmpeg.exe -i "input with spaces.mkv" -map 0:0 -map 0:1 \
    -c:a eac3 -ab 128k -ac 2 \
    -c:v libx264 -preset:v veryfast -tune:v animation -profile:v high -level:v 4.1 -b:v 3000k -strict -2 \
    -x264-params ref=4:subme=8:me_range=16:trellis=1:threads=18:lookahead_threads=3:bframes=3:keyint=240:keyint_min=24:rc_lookahead=50:ratetol=1.0:cplxblur=20.0:qblur=0.5 \

-vf "subtitles='input with spaces.mkv':si=0:force_style='Outline=1,Shadow=0'" output.mp4

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Encoding Video

Installing

Install FFmpeg with homebrew. You'll need to install it with a couple flags for webm and the AAC audio codec.

brew install ffmpeg --with-libvpx --with-libvorbis --with-fdk-aac --with-opus

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FFMpeg to Icecast2 Streaming Samples

Examples usage of various codecs with FFMpeg.

Samples

• flac.sh : An Icecast Source Client
  • for Windows (Cygwin is required)
  • and macOS (brew install ffmpeg)
• another_examples.sh : Samples
• FFMpeg can push to Icecast2 in various formats: Opus/Vorbis/AAC/MP3

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ffmpeg -y -i input.mp4 
-c:a libfaac -ac 2 -ab 192k -ar 44100 -c:v libx264 -profile:v high -level 4.0 -preset slow -b:v 3000k -maxrate 3000k -bufsize 3000k -filter:v scale=-1:720 -f mp4 -r 25 -g 25 -pix_fmt yuv420p encode_720high.mp4 
-c:a libfaac -ac 2 -ab 192k -ar 44100 -c:v libx264 -profile:v high -level 4.0 -preset medium -b:v 2000k -maxrate 2000k -bufsize 2000k -filter:v scale=-1:720 -f mp4 -r 25 -g 25 -pix_fmt yuv420p encode_720low.mp4 
-c:a libfaac -ac 2 -ab 160k -ar 44100 -c:v libx264 -profile:v main -level 3.0 -preset slow -b:v 1500k -maxrate 1500k -bufsize 1500k -filter:v scale=-1:576 -f mp4 -r 25 -g 25 -pix_fmt yuv420p  encode_576high.mp4
-c:a libfaac -ac 2 -ab 160k -ar 44100 -c:v libx264 -profile:v main -level 3.0 -preset fast -b:v 500k -maxrate 500k -bufsize 500k -filter:v scale=-1:576 -f mp4 -r 25 -g 25 -pix_fmt yuv420p  encode_576low.mp4
-c:a libfaac -ac 2 -ab 128k -ar 44100 -c:v libx264 -profile:v baseline -level 3.0 -preset slow -b:v 800k -maxrate 800k -bufsize 800k -filter:v scale=-1:288 -f 

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FFmpeg Walkthrough

basics

ffmpeg is a command line utility that presents a API to interacting with a variety of media types/encodings in a uniform fashion.

Depending on the ffmpeg distribiont, you may get access to utilities such as ffprobe (which provides information on a file) and ffplay (will play back a file). Those tools are critical.

Those tools, by default, will show all the arguments that ffmpeg was compiled with, which can get a little verbose. If you're going to run many ffmpeg commands, I suggest you get used to passing the -hide_banner argument.

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ffmpeg Cheat Sheet
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Lossless x264 compression:
ffmpeg -i capture1.00.avi -c:v libx264 -preset veryslow -crf 0 -c:a flac -compression_level 12 capture1.mkv

Lossless x265 compression:
ffmpeg -i capture1.00.avi -c:v libx265 -preset veryslow -x265-params lossless=1 -c:a flac -compression_level 12 capture1.mkv

Lossless compress audio in a video file:
ffmpeg -i capture1.00.avi -c:v copy -c:a flac -compression_level 12 capture1.mkv