What is Bitrate?
Bitrate measures how much audio data is encoded per second, expressed in kilobits per second (kbps). Higher bitrates preserve more audio detail but create larger files—the fundamental tradeoff in podcast audio optimization.
Understanding Bitrate
The math:
File Size = Bitrate × Duration
Example: 128 kbps × 3600 seconds (1 hour) = 460,800 kilobits = 57.6 MB
Bitrate Reference Chart
| Bitrate | Quality Level | File Size (1 hr) | Best For |
|---|---|---|---|
| 32 kbps | Very low | 14 MB | Voice memos, not recommended |
| 64 kbps | Acceptable mono | 29 MB | Solo speech, tight bandwidth |
| 96 kbps | Good mono/low stereo | 43 MB | Most speech podcasts |
| 128 kbps | Standard stereo | 58 MB | General podcasts |
| 160 kbps | Good stereo | 72 MB | Music with speech |
| 192 kbps | High quality | 86 MB | Music-focused content |
| 256 kbps | Very high | 115 MB | Critical listening, audiophile |
| 320 kbps | Maximum MP3 | 144 MB | Overkill for podcasts |
Mono vs Stereo Bitrates
A mono 64 kbps file can sound as good as a stereo 128 kbps file because:
- Mono uses all bits for one channel
- Stereo splits bits between two channels
- Speech podcasts rarely benefit from stereo positioning
Equivalent quality:
| Mono | Stereo Equivalent |
|---|---|
| 64 kbps | 128 kbps |
| 96 kbps | 192 kbps |
Constant vs Variable Bitrate
CBR (Constant Bitrate)
- Same bitrate throughout the file
- Predictable file sizes
- Slightly larger files
- More compatible with streaming
VBR (Variable Bitrate)
- Bitrate varies with audio complexity
- Smaller files at equivalent quality
- Silence uses fewer bits, complex audio uses more
- Slightly less compatible with some older apps
Why It Matters
Bitrate directly impacts three things listeners care about: audio quality, download speed, and data usage. Finding the right bitrate means delivering quality without wasting bandwidth.
Why bitrate optimization matters:
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Download completion: Large files = more abandoned downloads, especially on mobile networks.
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Storage constraints: Listeners with limited phone storage appreciate reasonable file sizes.
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Bandwidth costs: Higher bitrates cost more in CDN bandwidth fees for you.
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Quality floor: Too-low bitrates make voices sound muffled or robotic.
The 128 kbps myth: Many podcasters default to 128 kbps stereo without considering whether they need it. For a single-voice podcast, 64-96 kbps mono sounds identical and cuts file sizes in half.
Bitrate decision framework:
| Question | Yes → Higher Bitrate | No → Lower is Fine |
|---|---|---|
| Do you have music segments? | ✓ | |
| Are you stereo (sound effects, spatial audio)? | ✓ | |
| Do listeners report quality issues? | ✓ | |
| Is bandwidth cost a concern? | ✓ | |
| Are most listeners on mobile data? | ✓ |
The quality ceiling: Above 192 kbps for speech or 256 kbps for music, listeners cannot perceive quality improvements. Those extra bits are wasted bandwidth.
How to Use This in Dispatch
Audio is automatically encoded at optimal bitrates based on your content type:
Default optimization:
- Speech podcasts: 96-128 kbps (mono/stereo)
- Music podcasts: 192 kbps stereo
- Maximum quality preserved at reasonable file sizes
Customize encoding:
- Go to Show Settings → Audio
- Select your preferred bitrate
- Choose mono or stereo output
- New uploads encode with these settings
Re-encoding existing episodes: If you change settings, you can re-process existing episodes to apply new bitrate settings to your back catalog.
File size estimates: When uploading, you'll see estimated file sizes at different bitrates to help you make informed choices.