Transcoding and proxy generation
Transcoding is the direct digital-to-digital conversion of one encoding to another, if the file comes in an unwanted or unsupported encoding, or within the same encoding, for compressing or scaling reasons. Medialoopster automatically transcodes the asset's HighRes at creating a new asset (with the exception of recursive watchfolders where "in_place" is set to true):
- video: if a transcoding profile is added
- audio: to AIFF format, only if
settings.TRANSCODE_AUDIO_ON_UPLOAD = True. - image: usually a copy of the original media file
Proxy generation is another form of transcoding, issued automatically when creating a new audio/video asset, or requested manually via the administration interface (at "Video assets" → "Generate proxy for selected assets"). It generates the following files:
- proxy: a lower resolution version of the HighRes, for the display and play in the browser, to minimize the amount of data transferred during asset play
- image: PNG format, defined by
settings.PROXY_DEFAULT_IMAGE_EXT = ["png"]- an original PNG file will be herewith only rescaled
- audio: MP3 format and PNG synthesized waveform image, defined by
settings.PROXY_DEFAULT_AUDIO_EXT = ["mp3", "png"] - video: MP4 format, defined by
settings.PROXY_DEFAULT_VIDEO_EXT = ["mp4"]- at the manual proxy generation request, you can choose between MP4, OGV or WEBM formats
- image: PNG format, defined by
- PNG thumbnail
- shots and their PNG thumbnails, for video assets
Transcoding Settings (Optional)
If a transcoding device did not allow direct writing, which is checked in the device_profiler the profiler try to get an alternative device for buffered writing.
You can specify one fall back device by name which allows buffered writing within the settings.
BUFFERED_TRANSCODING_DEVICE = "example_device"
The assigned value must be a string.
Transcoding video profile
You must add at least one transcoding profile via the administration interface, then add the profile to the necessary devices at their "Transcoding profile" field, or set instead the below "Default profile" to true. The following is our example profile for video transcoding to MXF formats:
| Name | Required | Recommended value |
|---|---|---|
Name | yes | XDCAMHD422 MXF |
Codec name | no | mpeg2video |
Codec profile | no | xdcamhd422 |
Video container | no | mxf |
Frame rate | no | 25 |
| Video data rate | no | |
| Width | yes | 1920 |
| Height | yes | 1080 |
| Display aspect ratio | no | 16:9 |
| Pix fmt | no | |
| Progressive | no | |
| Passthrough | no | checked |
| Default profile | no | |
| Interlaced | yes | Top Field First |
| Ar conversion | yes | Squeezed |
| Should have audio | no | checked |
| Audio codec name | no | pcm_s16le |
| Audio container | no | |
| Audio codec profile | no | |
| Audio data rate | no | |
| Tracks | yes | 8 |
| Channels per track | yes | 1 |
| Bits per sample | yes | 16 |
| Sample rate | yes | 48000 |
Records of transcoding and proxy activities
In the above links you can see the records of ongoing or finalized transcoding and proxy activities, requested manually or happening automatically at asset creation.
In the administration interface the models are to be used only for visualizing.