Encoding Guidance
Accepted file formats: You can publish with the following file formats on Castos:
- Audio: .mp3, .aac, and .m4a
- Video: .mp4
Castos does not do any post-processing on uploaded files.
| Jump to: | Audio encoding |
|---|---|
| Video encoding |
Audio encoding
Export Settings
The export settings that we recommend for all of your audio files are:
- File Formats: .mp3, .aac, and .m4a
- Bitrate:128 kbps
- Mono or Stereo: Mono is usually sufficient if it's just spoken word, but if you have sound effects then Stereo is a nice touch.
The bitrate that you export your files at is a balance between creating a really high fidelity file with a file size that's reasonable for your audience to download or stream. The highest fidelity file may have a slight increase in quality of sound, but will take too long for your audience to download. If the file is smaller it will download more quickly but will sacrifice a bit of audio quality along the way. The 128 kbps bitrate is a nice compromise between those two concerns.
Here's just a few other additional settings you may find in your audio editing software:
- Sample Rate: 44.1 kHz
- Bit Depth: 32-bit float or 24-bit
- .mp3 Type: Constant Bit Rate (CBR)
What about loudness?
If you've ever switched from one podcast to another and noticed that one was waaaaay louder than the next then you've encountered inconsistent loudness settings. Loudness is the volume at which your files are exported, and should be benchmarked against these industry standards:
- Mono: -19 LUFS (this is the same perceived loudness as -16 LUFS for stereo)
- Stereo: -16 LUFS
Video encoding
File Formats: .mp4
Important: Unlike video platforms like YouTube, which automatically adjust video resolution based on a viewer’s internet speed, video files in podcast RSS feeds are downloaded or streamed in their full resolution, regardless of the listener’s connection quality.
What does this mean for you? If a video podcast episode has a large file size, listeners with slower internet connections or limited data may experience long download times, significant lag, or high data consumption. For podcast creators, it’s important to carefully consider video file sizes to ensure a better user experience across a variety of connection speeds and devices.