Transcoding Methodology

podkit’s goal is to get your media onto your iPod at the best possible quality. It only transcodes what it needs to — compatible files are copied as-is, and output quality is never higher than the source.

Core Principles

Only Transcode What’s Necessary

Not every file needs transcoding. podkit categorizes each source file and takes the minimum action:

Source Type	Examples	What Happens
Lossless	FLAC, WAV, AIFF, ALAC	Transcoded to your chosen preset
Compatible lossy	MP3, M4A (AAC)	Copied directly — no re-encoding
Incompatible lossy	OGG, Opus	Transcoded + lossy-to-lossy warning

Why copy compatible lossy files? Re-encoding MP3 to AAC only loses quality. Even “upconverting” 128 kbps MP3 to 256 kbps AAC wastes space without improving audio. podkit avoids this entirely.

Source Quality Awareness

podkit analyzes source files and caps output quality accordingly. Low-quality sources won’t be wastefully upscaled:

Source Quality	Your Setting	Effective Output
High-quality source	high	Full quality at preset bitrate
Low-quality source	high	Capped to source quality

This applies to both audio and video. For video, resolution is also matched to device capabilities — a 1080p source is scaled down to 640x480 for iPod Classic, not upscaled.

Lossy-to-Lossy Warnings

When podkit encounters incompatible lossy files (OGG, Opus) that must be re-encoded, it warns you during --dry-run. This is an unavoidable quality trade-off — you can decide whether to accept it or convert those files to a compatible format beforehand.

Passthrough

If a file is already fully compatible with the target device, podkit copies it without any processing. For audio, this means MP3 and AAC files. For video, this means H.264/AAC in an MP4/M4V container that fits within the device’s resolution and bitrate limits.

The dry run shows what will happen to each file:

+ [transcode    ] Artist - Song.flac
+ [copy         ] Artist - Track.mp3
+ [transcode    ] Movie.mkv
+ [passthrough  ] Compatible.m4v

Metadata Preservation

podkit preserves metadata through transcoding:

• All standard tags (title, artist, album, track number, disc number, year, genre)
• Album artwork (embedded in output file)
• Video content type detection (movie vs. TV show)

Quality Configuration

Audio and video quality use a unified system. The quality field sets both audio and video quality, while audioQuality and videoQuality let you override each independently:

# Global unified quality (audio + video)
quality = "high"

# Or override audio and video separately
audioQuality = "lossless"
videoQuality = "medium"

# Per-device overrides
[devices.classic]
quality = "high"
audioQuality = "lossless"     # Lossless audio on Classic
videoQuality = "high"

[devices.nano]
quality = "medium"            # Both audio and video use medium

# Environment variables
export PODKIT_QUALITY=medium
export PODKIT_AUDIO_QUALITY=high
export PODKIT_VIDEO_QUALITY=low

# Command-line overrides
podkit sync --quality medium
podkit sync --audio-quality lossless --lossy-quality max
podkit sync --video-quality low

Audio and video have separate quality presets suited to their formats. See the detailed guides:

• Audio Transcoding — AAC presets, VBR vs CBR, encoder selection, file size estimates
• Video Transcoding — Device profiles, resolution handling, H.264 settings, hardware acceleration