Why is the audio out of sync after converting?

Common causes: (1) variable framerate source rendered as constant (use -vsync vfr to preserve VFR); (2) different audio sample rates not resampled (add -ar 48000 ); (3) container limitations (MP4 with variable framerate misbehaves — prefer MKV during editing, encode to MP4 only at the end). Always run ffprobe on both source and output to compare timing.

Why is the audio out of sync after converting?

Common causes: (1) variable framerate source rendered as constant (use -vsync vfr to preserve VFR); (2) different audio sample rates not resampled (add -ar 48000 ); (3) container limitations (MP4 with variable framerate misbehaves — prefer MKV during editing, encode to MP4 only at the end). Always run ffprobe on both source and output to compare timing.

Guide

AVI Video Format: Complete Guide — What It Is, How to Convert It

PC By Pablo Cirre • Updated May 7, 2026

AVI Video Format: Complete Guide

AVI — Audio Video Interleave — is one of the oldest container formats for digital video. Introduced by Microsoft in November 1992 as part of the Video for Windows framework, it was designed to store synchronized audio and video streams in a single file. Thirty years later, AVI files are still everywhere: on old hard drives, in digital cameras from the 2000s, on surveillance systems, and in legacy editing pipelines.

What Is an AVI File?

AVI is a container format, not a codec. The .avi extension tells you about the wrapper, not the compression used inside. A single AVI file can contain:

Video streams: DivX, Xvid, H.264, MPEG-4 Part 2, MPEG-2, Cinepak, Indeo, or uncompressed video
Audio streams: MP3, PCM (uncompressed), AC3, AAC, or WMA
Subtitle tracks: limited support (OpenDML extension)

This flexibility is both a strength and a weakness. An AVI with H.264 video and MP3 audio is nearly identical to an MP4 with the same streams — the difference is just the container metadata.

Technical Specifications

Property	Details
Full name	Audio Video Interleave
Extension	`.avi`
MIME type	`video/x-msvideo`
Introduced	1992 (Microsoft)
Max file size	2 GB (original) / virtually unlimited (OpenDML/AVI 2.0)
Max resolution	Depends on codec — up to 4K with H.264
Streaming	Poor — not designed for HTTP streaming
Chapters	Not supported
Subtitles	External only (original spec)

AVI vs MP4 vs MKV

Feature	AVI	MP4	MKV
Age	1992	2001	2002
Streaming	❌ Poor	✅ Excellent	⚠️ Limited
Chapters	❌ No	✅ Yes	✅ Yes
Subtitles	❌ External	✅ Embedded	✅ Multiple tracks
Browser playback	❌ No	✅ Yes	❌ No
Max file size	⚠️ 2 GB (old)	✅ Unlimited	✅ Unlimited
Codec support	Medium	Wide	Widest
Universal player	✅ Very high	✅ Very high	✅ High

Software That Opens AVI Files

Windows: Windows Media Player, VLC, MPC-HC, PotPlayer macOS: VLC (QuickTime may fail depending on codec), IINA Linux: VLC, mpv, Totem Mobile: VLC for Android/iOS, MX Player Online: KaijuConverter, CloudConvert

If an AVI file refuses to play, the problem is almost always the codec, not the container. Installing the K-Lite Codec Pack (Windows) or using VLC (cross-platform) resolves 95% of playback issues.

How to Convert AVI to MP4 (FFmpeg)

# Fast re-mux — no re-encoding (only works if video is already H.264)
ffmpeg -i input.avi -c:v copy -c:a copy output.mp4

# Full re-encode to H.264 + AAC (maximum compatibility)
ffmpeg -i input.avi -c:v libx264 -preset slow -crf 22 -c:a aac -b:a 192k output.mp4

# Re-encode for web (add faststart for streaming)
ffmpeg -i input.avi -c:v libx264 -preset slow -crf 22 \
       -c:a aac -b:a 192k -movflags +faststart output.mp4

# Convert to H.265/HEVC for smaller files (modern devices)
ffmpeg -i input.avi -c:v libx265 -crf 28 -c:a aac -b:a 192k output.mp4

How to Convert AVI to MKV

# Re-mux without quality loss (keeps original codec)
ffmpeg -i input.avi -c copy output.mkv

# Re-encode to H.264 inside MKV
ffmpeg -i input.avi -c:v libx264 -crf 22 -c:a libmp3lame -q:a 2 output.mkv

Batch Convert AVI to MP4 (All Files in a Folder)

# Linux / macOS
for f in *.avi; do
  ffmpeg -i "$f" -c:v libx264 -crf 22 -c:a aac -b:a 192k "${f%.avi}.mp4"
done

# Windows PowerShell
Get-ChildItem *.avi | ForEach-Object {
  ffmpeg -i $_.FullName -c:v libx264 -crf 22 -c:a aac -b:a 192k ($_.BaseName + ".mp4")
}

Why AVI Files Are So Large

AVI files are often much larger than equivalent MP4/MKV files for several reasons:

Uncompressed or lightly compressed audio — PCM audio adds ~10 MB per minute
Older, less efficient codecs — Xvid and DivX compress less than H.264 or H.265
Padding bytes — the AVI format adds interleave padding for seeking
No B-frames in some profiles — reduces compression efficiency

Converting to H.264 in an MP4 container typically reduces file size by 30–60% with no perceptible quality loss.

Common AVI Problems and Fixes

Problem	Cause	Fix
"Codec not found" error	Missing codec pack	Install VLC or K-Lite
Audio out of sync	Bad interleave	Re-encode with FFmpeg
File stops at 2 GB	Old format limit	Check if OpenDML extension is used
No subtitles	Container limitation	Use MKV instead
Won't play on phone	DivX/Xvid not supported	Convert to H.264 MP4

When to Keep AVI vs Convert

Keep AVI when:

The file is already high quality and you don't need to re-encode
You're working in a legacy editing environment that requires AVI
You just need to archive the file and storage isn't a concern

Convert to MP4 when:

You want to play it on a phone, TV, or share online
You want smaller file sizes
You need streaming or web playback

Convert to MKV when:

You want multiple audio tracks or subtitle tracks
You're archiving video with maximum codec flexibility

Related conversions

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Frequently Asked Questions

AVI (Audio Video Interleave) and MP4 (MPEG-4 Part 14) are both container formats, but MP4 is more modern. MP4 supports HTTP streaming (with -movflags faststart), embedded subtitles, chapters, and achieves smaller file sizes with H.264 or H.265 video. AVI was designed in 1992 and lacks native streaming support, but is still widely playable on legacy software.

AVI (Audio Video Interleave) e MP4 (MPEG-4 Part 14) are both container formatoos, mas MP4 is more moderno. MP4 suporta HTTP streaming (with -movflags faststart), embedded subtitles, chapters, e achieves smaller tamanho do arquivos com H.264 ou H.265 video. AVI was designed in 1992 e lacks native streaming support, mas is still widely playable on legacy software.

AVI (Audio Video Interleave) und MP4 (MPEG-4 Part 14) are both Container Formate, aber MP4 is more modern. MP4 unterstützt HTTP streaming (with -movflags faststart), embedded subtitles, chapters, und achieves smaller Dateigrößes mit H.264 oder H.265 video. AVI was designed in 1992 und lacks native streaming support, aber is still widely playable on legacy Software.

AVI (Audio Video Interleave) y MP4 (MPEG-4 Part 14) are both contenedor formatoos, pero MP4 is more moderno. MP4 soporta HTTP streaming (with -movflags faststart), embedded subtitles, chapters, y achieves smaller tamaño de archivos con H.264 o H.265 video. AVI was designed in 1992 y lacks native streaming support, pero is still widely playable on legacy software.

AV1 is the most efficient (royalty-free, ~30% smaller than H.265) but encoding is slow. H.265 (HEVC) saves ~30–50% over H.264 and is supported by every modern phone and desktop. H.264 remains the safest baseline for legacy compatibility. Rule of thumb: archives → AV1, daily use → H.265, broadest reach → H.264.

AVI files tend to be large for three reasons: (1) they often contain uncompressed PCM audio rather than compressed MP3 or AAC, (2) older codecs like DivX or Xvid compress less efficiently than modern H.264 or H.265, and (3) the AVI format adds interleave padding. Converting to H.264 in MP4 typically reduces size by 30–60% with no visible quality loss.

AVI arquivos tend to be large para three reasons: (1) they often contain não comprimido PCM audio em vez de comprimido MP3 ou AAC, (2) older codecs like DivX ou Xvid compress less efficiently than moderno H.264 ou H.265, e (3) the AVI formato adds interleave padding. convertendo to H.264 in MP4 tipicamente reduces size by 30–60% com no visible quality loss.

AVI Dateien tend to be large für three reasons: (1) they often contain uncompressed PCM audio rather than komprimiert MP3 oder AAC, (2) older Codecs like DivX oder Xvid compress less efficiently than modern H.264 oder H.265, und (3) the AVI Format adds interleave padding. umwandelnd to H.264 in MP4 typically reduces size by 30–60% mit no visible quality loss.

AVI archivos tend to be large para three reasons: (1) they often contain uncompressed PCM audio rather than comprimido MP3 o AAC, (2) older codecs like DivX o Xvid compress less efficiently than moderno H.264 o H.265, y (3) the AVI formato adds interleave padding. convirtiendo to H.264 in MP4 typically reduces size by 30–60% con no visible quality loss.

CRF (Constant Rate Factor) is the best default for offline files: ffmpeg picks the bitrate frame-by-frame to maintain perceived quality. Two-pass is only better when you must hit an exact final size (DVD targets). Constant bitrate is for streaming with a fixed channel. For "smallest at quality X" always use CRF.

Yes. VLC Media Player handles virtually all AVI files regardless of the internal codec (DivX, Xvid, H.264, Cinepak, Indeo, etc.) because it bundles its own codec libraries. If Windows Media Player or QuickTime cannot open an AVI, VLC is the recommended free alternative.

Yes. VLC Media Player handles virtually all AVI arquivos regardless of the internal codec (DivX, Xvid, H.264, Cinepak, Indeo, etc.) because it bundles its own codec libraries. If Windows Media Player ou QuickTime cannot abrir an AVI, VLC is the recommended grátis alternative.

Yes. VLC Media Player handles virtually all AVI Dateien regardless des internal Codec (DivX, Xvid, H.264, Cinepak, Indeo, etc.) because it bundles its own Codec libraries. If Windows Media Player oder QuickTime cannot öffnen an AVI, VLC is the recommended kostenlos alternative.

Yes. VLC Media Player handles virtually all AVI archivos regardless del internal codec (DivX, Xvid, H.264, Cinepak, Indeo, etc.) because it bundles its own codec libraries. If Windows Media Player o QuickTime cannot abrir an AVI, VLC is the recommended gratis alternative.

Common causes: (1) variable framerate source rendered as constant (use <code>-vsync vfr</code> to preserve VFR); (2) different audio sample rates not resampled (add <code>-ar 48000</code>); (3) container limitations (MP4 with variable framerate misbehaves — prefer MKV during editing, encode to MP4 only at the end). Always run <code>ffprobe</code> on both source and output to compare timing.

Use FFmpeg with the copy codec if your AVI already contains H.264 video: ffmpeg -i input.avi -c copy output.mp4. This re-muxes in seconds with zero quality loss. If the video uses an older codec like DivX or Xvid, re-encode with: ffmpeg -i input.avi -c:v libx264 -crf 18 -c:a aac output.mp4. CRF 18 is near-lossless visually.

Use FFmpeg com the copy codec if your AVI already contém H.264 video: ffmpeg -i input.avi -c copy output.mp4. This re-muxes in seconds com zero quality loss. If the video uses an older codec like DivX ou Xvid, re-encode with: ffmpeg -i input.avi -c:v libx264 -crf 18 -c:a aac output.mp4. CRF 18 is near-lossless visually.

Use FFmpeg mit the copy Codec if your AVI already contains H.264 video: ffmpeg -i input.avi -c copy output.mp4. This re-muxes in seconds mit zero quality loss. If the video uses an older Codec like DivX oder Xvid, re-encode with: ffmpeg -i input.avi -c:v libx264 -crf 18 -c:a aac output.mp4. CRF 18 is near-lossless visually.

Use FFmpeg con the copy codec if your AVI already contains H.264 video: ffmpeg -i input.avi -c copy output.mp4. This re-muxes in seconds con zero quality loss. If the video uses an older codec like DivX o Xvid, re-encode with: ffmpeg -i input.avi -c:v libx264 -crf 18 -c:a aac output.mp4. CRF 18 is near-lossless visually.

Yes if you only change the container: <code>ffmpeg -i in.mkv -c copy out.mp4</code>. This remuxes the stream without re-encoding, takes seconds even for hours of footage. Limitations: codec must be supported by the target container (e.g. you cannot put H.264 in WebM, only VP8/VP9/AV1). To shrink size you must re-encode.