How to Convert RMVB to MP4 Freely for More Devices
RMVB was quite popular for a time to spread TV and movie videos online, especially in Asian. Although RMVB file can be played on Windows (10) PC or macOS by using RealPlayer, Media Player Classic or VLC media player, it's still a troublesome stuff to play RMVB on iOS, Android, smart TV, Xbox, PSP and more programs unless third-party RMVB player is installed beforehand. To make RMVB friendly to all of your player screens, the best way is to convert RMVB to MP4.
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Convert RMVB to MP4 with WinX HD Video Converter Deluxe
- Supported OS: Windows 10, Windows 8.1/8/7, macOS
- Average User Rating: ★★★★☆
WinX HD Video Converter Deluxe - An all-in-one RMVB video converter that perfectly supports converting video from RMVB to MP4, AVI, MOV, FLV, WebM, MP3, iPhone, iPad, Android, YouTube, Chromecast, gaming consoles etc. By taking the full use of multiple CPU cores, QSV and CUDA/NVENC hardware acceleration, this tool is able to transcode RMVB to MP4 at advanced 16x faster speed stably.
Steps to Fast Convert RMVB to MP4 with High Quality
Preparation: Free download WinX RMVB Video Converter and install it on your computer.
Step 1. Select and open one or more RMVB files from computer with WinX HD Video Converter Deluxe by clicking "+ video" icon or direct drag-and-drop.
Step 2. Choose "MP4 H264" from Video tab on the bottom of the interface. Also, you can click Target Format button to get full output profiles (where 420+ preset profiles are provided).

Step 3. Press "RUN" button to let the software start to convert RMVB to MP4 in accelerated speed.
Generally, there's no need to do other settings. But if you really want to edit video resolution/bit rate/aspect ratio/subtitles, crop/trim video and more, just do it under "Edit" and "Codec Option" functions. Another tip is when you check "Merge" option in the right panel, your RMVB video clips can be batch converted into a single MP4.
How to Convert RMVB to MP4 using Handbrake
HandBrake can handle the RMVB to MP4 conversion. However, the open source RMVB to MP4 converter freeware may produce a problematic MP4 video like: "It plays fine in the beginning, but as the video progresses, the video and audio tend to become more and more out-of-sync." "What's happening is I have some RMVB files as source videos, I converted the files to iPhone format MP4 using HB, but when I play the files on iPhone I get no sound." If you still want to use Handbrake, refer to how to convert video with Handbrake.

Convert RMVB to MP4 Free Online using Web-based Services
There are quite many online RMVB to MP4 video converters that seem to be convenient. Just open the website, choose video files, and click convert. Top-rated free online RMVB converters include CloudConvert, FreeConvert, Zamzar, and Convertio.
Cons: such free online RMVB to MP4 converter tools actually have more or less requirements, like providing your email address, signing up the site, 200MB maximum RMVB file size... Moreover, their web pages may contain some annoying ads, pop-ups, or even harmful malware.

Verdict
Taking all factors(quality, speed, file size limit, safety) into consideration, clean and safe desktop-based WinX HD Video Converter Deluxe is your ideal choice for a much faster and faultless RMVB to MP4 conversion, skipping over the "(RMVB) upload and (MP4) download" process, avoiding transcoding RMVB into a defective MP4. Free online tools are only suitable for users who have RMVB video files less than 200MB.
Learn More about RMVB
RMVB, full name RealMedia Variable Bitrate with ".rmvb" file extension, is an advanced container format developed by RealNetworks after RM and usually used for storing multimedia content locally. Thanks to the support for VBR, RMVB can pretend video with clearer image than (CBR-ed) RM by reducing bitrate in static pictures while raising bitrate automatically in complicated dynamic pictures, e.g the scenes of fighting, dancing and racing, achieving as distinctive and fluent visual experience as possible.
RMVB-formatted movie videos were quite common to see via BitTorrent and eDonkey, to deliver compressed DVD movies and TV episodes in 1280x720 at most. But gradually, MP4/X264 has overtaken it with higher compression and better device compatibility. So if you happen to wanna watch your local out-dated RMVB files on your modern gadgets, you'd better convert RMVB to MP4 in advance.