Membrane.FFmpeg.Transcoder

Membrane plugin to transcode video into different qualities using FFmpeg.

Requirements

• ffmpeg

Usage

Basic Multi-Quality Transcoding

spec = [
  child(:source, %Membrane.File.Source{location: "input.ts"})
  |> child(:transcoder, Membrane.FFmpeg.Transcoder)
  |> via_out(:video, options: [resolution: {-2, 1080}, bitrate: 6_500_000, fps: 30])
  |> child(:hd_sink, %Membrane.File.Sink{location: "hd.h264"}),

  get_child(:transcoder)
  |> via_out(:video, options: [resolution: {-2, 720}, bitrate: 3_300_000, fps: 30])
  |> child(:sd_sink, %Membrane.File.Sink{location: "sd.h264"}),

  get_child(:transcoder)
  |> via_out(:audio, options: [bitrate: 128_000, sample_rate: 48_000, channels: 2])
  |> child(:audio_sink, %Membrane.File.Sink{location: "audio.aac"})
]

Stream Copy (No Re-encoding)

spec = [
  child(:source, %Membrane.File.Source{location: "input.ts"})
  |> child(:transcoder, Membrane.FFmpeg.Transcoder)
  |> via_out(:video, options: [copy: true])
  |> child(:video_sink, %Membrane.File.Sink{location: "video.h264"}),

  get_child(:transcoder)
  |> via_out(:audio, options: [copy: true])
  |> child(:audio_sink, %Membrane.File.Sink{location: "audio.aac"})
]

MP4 Output with Parsers

spec = [
  child(:source, %Membrane.File.Source{location: "input.ts"})
  |> child(:transcoder, Membrane.FFmpeg.Transcoder)
  |> via_out(:video, options: [resolution: {-2, 720}, bitrate: 3_300_000])
  |> child(:h264_parser, %Membrane.H264.Parser{output_stream_structure: :avc1})
  |> child(:mp4_muxer, %Membrane.MP4.Muxer.ISOM{fast_start: true})
  |> child(:sink, %Membrane.File.Sink{location: "output.mp4"})
]

Teletext Subtitle Extraction

spec = [
  child(:source, %Membrane.File.Source{location: "input_with_teletext.ts"})
  |> child(:transcoder, Membrane.FFmpeg.Transcoder)
  |> via_out(:text, options: [source: {:dvb_teletext, 777}])
  |> child(:subtitle_sink, %Membrane.Testing.Sink{})
]

Video Options

• resolution: {width, height} (use -2 for auto-calculated dimension)
• bitrate: Maximum bitrate in bits/second
• fps: Target framerate
• profile: :baseline, :main, :high
• crf: Constant rate factor (18-28, lower = higher quality)
• preset: :ultrafast, :veryfast, :fast, :medium, :slow
• tune: :zerolatency, :film, :animation
• gop_size: GOP size in frames
• b_frames: Number of B-frames
• copy: Skip re-encoding (boolean)

Audio Options

• bitrate: Target bitrate in bits/second
• sample_rate: Sample rate in Hz
• channels: Number of audio channels
• copy: Skip re-encoding (boolean)

Features

• buffers come with pts and dts values
• same performance as ffmpeg
• simple API: attach an output with options, that's it (check the test)
• constrains the bitrate
• by adding a Membrane.h264.Parser in the middle, it is compatible with Membrane.MP4.Muxer.CMAF and Membrane.MP4.Muxer.ISOM
• transcodes to AAC and H264

Copyright and License

Copyright 2024, KIM Keep In Mind GmbH Licensed under the Apache License, Version 2.0