Why quicktime not playing mp4 files on mac and windows pc?

QuickTime player does not support MP4 video files with VP09 codecs. No worries. You can convert the mp4 video to QuickTime player compatible codes such as H.264 or H.265.

The issue you're experiencing with QuickTime not playing MP4 files is likely due to the specific codecs used in the video file. QuickTime Player natively supports certain codecs, and when a file uses incompatible codecs like VP09 (VP9) or certain audio codecs, it may fail to play.

Why QuickTime not Playing MP4 files:

• VP09 (VP9) Codec: QuickTime has limited support for VP9, which is a newer video codec primarily supported in browsers and some media players but not fully in QuickTime.
• MPEG-4 HE AAC: AAC audio is generally supported, but combined with an unsupported video codec, playback issues can occur.
• File from Bluesky app: The app may be encoding or packaging videos with newer or less compatible codecs.

QuickTime on Mac is more limited, but ensure your system is updated, or consider installing Perian (though outdated), or use native apps like Preview or Safari for web-based playback.

VP9 is an open and royalty-free video codec developed by Google as a successor to VP8. It is designed to deliver high-quality video compression that rivals or even exceeds the efficiency of H.265/HEVC, making it especially popular for web streaming platforms like YouTube. VP9 supports resolutions up to 8K, variable bitrate encoding, and is optimized for reducing bandwidth consumption while maintaining visual quality, which is particularly useful for streaming over slower internet connections.

Despite its advantages, VP9 faces several challenges. One major issue is limited hardware support. Not all devices or GPUs are capable of decoding VP9 efficiently, especially older or low-end systems. This means that some users may experience playback issues, such as stuttering or increased CPU usage, when watching VP9-encoded videos. Additionally, Apple devices, including Safari and QuickTime Player, do not natively support VP9, favoring H.264 and HEVC instead. This means QuickTime can't play mp4 files on mac with VP09 encoding. This lack of broad compatibility can make VP9 inconvenient for content creators targeting a diverse audience.

Another challenge lies in software tool support and editing compatibility. Many professional video editing tools and media players either do not support VP9 or handle it poorly. This makes post-processing and playback less convenient.

You're wondering if messing around with QuickTime not playing MP4 on Mac or trying to fix the MP4 playback issue is risky? I’ve been there myself, and honestly, it’s usually pretty safe to tinker with QuickTime settings or even reinstall it if needed — as long as you get the official version from Apple.

Here’s my take based on my own experience:  

• QuickTime is pretty straightforward. If QuickTime not playing MP4 on Mac, it’s often a codec problem or a glitch.
• Usually, uninstalling and reinstalling QuickTime (or updating it) helps. No biggie there.
• Just make sure to get the official installer from Apple’s website. Avoid shady sources, because you don’t want malware sneaking in.

Potential risks:  

• If you’re trying to tweak system codecs or mess with system files, that’s where things can go sideways.
  But for QuickTime itself, just reinstalling or updating it is generally safe.
• Also, avoid messing with registry entries or system files unless you’re super confident — that can cause more headaches.

If QuickTime not playing MP4 files on your Mac or Windows PC and you're looking for a free solution, here are some steps and alternative options you can try:

What should you if Quicktime not playing MP4:

• Update QuickTime: Ensure you have the latest version of QuickTime installed (For Mac).
• Check the MP4 Codec: Sometimes, QuickTime may not support certain codecs inside MP4 files. You can verify this with a media info tool like MediaInfo (For Mac).
• Update QuickTime: If you still want to troubleshoot QuickTime, ensure it’s up-to-date (for Windows computer).

1. Use Built-in Media Players (Windows & Mac)
Windows: The default Movies & TV app or Windows Media Player can often handle MP4 files. 
Mac: The default QuickLook or Preview might open some MP4 files, but if not, try other free players.

2. Use Free Open-Source Media Players
MPV Player: A lightweight, open-source media player that supports a wide range of formats.

3. Convert MP4 Files to a Compatible Format
Use HandBrake (free) to convert your MP4 to a format compatible with QuickTime.
* Download from HandBrake
* Open HandBrake, load your MP4, select a compatible format (like MOV or MP4 with supported codecs), and convert.

4. Check and Repair the MP4 File
Sometimes, MP4 files are corrupted or have incompatible codecs.
* Use MediaInfo to check the codecs used.
* If the file is damaged, try repairing with tools like FFmpag (free, command-line) or online repair services.

MPEG-4 HE AAC and vp09 refer to specific types of audio and video codecs commonly used in streaming media.

What is MPEG-4 HE AAC?

HE-AAC (High-Efficiency Advanced Audio Coding) is an audio codec that is an extension of the regular AAC format.

It’s designed to deliver high audio quality at low bitrates, making it popular in streaming (like YouTube or internet radio).

It’s also known as AAC+, and includes tools like Spectral Band Replication (SBR) to improve compression.

What is vp09?

vp09 is a video codec developed by Google, also known as VP9.

It is a successor to VP8 and an open-source competitor to H.265/HEVC.

VP9 is commonly used on YouTube and other web platforms to stream high-resolution videos efficiently.

Why QuickTime Player can't play mp4 on mac

1. Lack of native support:

QuickTime Player on Mac doesn't support VP9 (vp09) video codec natively.

It also may struggle with HE-AAC in certain MPEG-4 containers if the file isn’t formatted properly.

2. Format container incompatibility:

If the video is in a WebM or a non-standard MP4 container using vp09, QuickTime won’t recognize the stream correctly.