Converting From .FLV to .MP4 and Other Formats using FFmpeg on Windows

After a hair-pulling couple of hours trying to figure out how to conveniently convert .flv files into a more generally-accepted video format, I decided to write this brief guide to help anyone who may be experiencing a similar problem.

By default, OpenBroadcastSoftware (OBS) encodes recorded video in .flv format. This is unfortunate to anyone wanting to edit their latest footage in Windows Movie Maker or other common video editors, as the .flv file type does not fare well with these programs. Finding reliable, free video converting software online is a shot in the dark, and can oftentimes infect your computer with bloatware if not careful. There is no need to purchase any unnecessary software, just follow the steps below and you can convert .flv, among other files, quite fast for free through the command line.

This tutorial is intended for Windows 10, but will work on older versions of the operating system at the expense of the screenshots not matching perfectly. Similarly, different software may yield slightly inconsistent labeling, buttons, and locations of elements found within the screenshots. In this tutorial we will need to extract a .zip file, so necessary software is required. I recommend either 7zip or winRAR as they are lightweight with free trial versions. I am using winRAR, personally. There is a good chance you already have this extraction software on your PC.

Let's get started!

Download FFmpeg from Zeranoe.

Download FFmpeg from Zeranoe.

Step 1 - Download FFmpeg

The software we will be using is called FFmpeg and it can be found by clicking here. Click the big, blue Download FFmpeg button to start downloading the latest version, which at the time of this writing is 20172014-8fa18e0. Either the 32-bit or 64-bit architecture should be automatically selected based off what computer you are using, but if you encounter issues later in this tutorial it is a possibility you downloaded the incompatible architecture. If you want to determine whether your system is 32-bit or 64-bit, reference Steps 7 through 11 and then come back.


Open the .zip when the download has finished.

Open the .zip when the download has finished.

Step 2 - Open the Download

Once the file has completed its download, open it. Where you find this completed download is dependent on which browser is being using and what preferences you have set. For Google Chrome, my browser of choice, completed downloads appear at the bottom of the screen. You can also find a list of all downloads by pressing Ctrl + J on the keyboard.


Extract the .zip contents.

Extract the .zip contents.

Step 3 - Extracting the Files

Next, we need to extract the contents of the .zip. To do this, locate an Extract To button either in the upper navigation of the window that appears or by right-clicking the ffmpeg... folder and selecting the option from the popup list.


Change the extraction destination path to the root directory.

Change the extraction destination path to the root directory.

Step 4 - Selecting the Extraction Destination Path

We want to change the file extraction destination path to the root directory of the PC. Type C:\ in the Destination path field. Click OK.


Navigate to the root directory via Run.

Navigate to the root directory via Run.

Step 5 - Navigating to the Root Directory

After the extraction has completed, press the Windows Key + R and a Run dialogue box should appear. Type C:\ into the Open field and click OK.


Locate the extracted contents in the root directory.

Locate the extracted contents in the root directory.

Step 6 - Inside the Root Directory

You will now be in the root directory of your computer. Locate the folder named, in part, ffmpeg. If you cannot find it, ensure that you are in the root directory (C:\) and that you indeed extracted the contents of the .zip to it.


Rename the folder to "ffmpeg".

Rename the folder to "ffmpeg".

Step 7 - Rename the Folder

For simplicity's sake, we are going to rename the lengthy folder name to something that's easier to type. Right-click the folder and select Rename. Type in ffmpeg and press enter.


Open the Control Panel via Run.

Open the Control Panel via Run.

Step 8 - Navigating to the Control Panel

Similar to Step 5, we are going to press Windows Key + R to bring up the Run window. This time, however, we will type in control panel and then click OK.


Click on System and Security.

Click on System and Security.

Step 9 - System and Security

Click on System and Security in the Control Panel.


Click on System.

Click on System.

Step 10 - System

Locate System in the list of options and click it.


Click on Advanced System Settings on the left side-panel.

Click on Advanced System Settings on the left side-panel.

Step 11 - Advanced System Settings

You may notice some system information on the right of the window. Here, you can find out whether your system is 32-bit or 64-bit.

On the left side-panel, you will see Advanced system settings beside a shield. Click it.


Click on Environment Variables...

Click on Environment Variables...

Step 12 - System Properties

Towards the bottom of the new window that appear, click the button labeled Environment Variables...


Select Path in upper pane, User Variables, and then click Edit...

Select Path in upper pane, User Variables, and then click Edit...

Step 13 - Environment Variables

In the upper pane, User variables, you will see Path. Click that line and then Edit... beneath. If you cannot find Path, click New... 


Modify the variable value with the bin directory of ffmpeg.

Modify the variable value with the bin directory of ffmpeg.

Step 14 - Editing the User Variables

If you could not locate Path in the previous step, simply type Path into the top field, Variable name. In the second field, Variable value, type ;C:\ffmpeg\bin. Then, click OK. You can click the OK button on System Properties window as well.


Open Command Prompt via Run.

Open Command Prompt via Run.

Step 15 - Opening the Command Prompt

Similar to Steps 5 and 8, you will be opening Run again by pressing the Windows Key + R. Type cmd and click OK. Command prompt will open.


Change the directory to where your video is located.

Change the directory to where your video is located.

Step 16 - Command Prompt and Changing Directories

We want the command prompt to be able to locate the video we want to convert. Type cd ("change directory") and then the directory where your video is located, presumably Videos.

cd C:\Users\USER\Videos would bring us to the video folder, assuming USER is replaced with your user name, which is found to the left of the > on the line you are typing on right now.


Convert your .flv video to .mp4 using this command.

Convert your .flv video to .mp4 using this command.

Step 17 - Converting the Video

This is the last step, converting the video! You will want to type (or copy-paste) the code below, replacing input.flv with the name of the video you want to convert (input), and output.mp4 with what you want the converted video file to be named.

ffmpeg -i input.flv -c:v libx264 -crf 23 -strict experimental output.mp4

Press enter and wait for the video to convert. The new video will appear in the same directory as the input video.

To be more specific with what exactly what the command does, let's break down it down. ffmpeg allows us to conveniently reference the path to the program we set up in Step 14. Next, we have the input file, input.flv, followed by referencing the codec (data encoder and decoder), -c:v libx264-crf determines the level of output video quality, where the smaller the number the better the quality. 23 is the default quality level, and the common range is between 18 and high 20s. Finally, before the output name, we include -strict experimental which, in short, allows for us to use a sandboxed encoder to get this working.

FFmpeg is powerful and can be used to convert to file formats other than mp4, though the command will differ outside of simply changing the .mp4 extension, unfortunately. Luckily, it has rich documentation on all its functionalities.


Finishing Up and Troubleshooting

Hopefully you were able to successfully convert the video. If not, it may be a good idea to go back ensure you followed all the steps; it is easy to overlook something small! If you need additional help, you can check out the FFmpeg forums.

Thanks for reading this tutorial. If you have any questions, comments, or critiques, feel free to leave them below as always.