How to Render SFM to MP4: Image Sequences to Video With FFmpeg

FFmpeg is a free command-line tool. It reads numbered frames like shot_0000.tga, encodes them to H.264, and adds your sound track in one command.

This guide covers the export, the FFmpeg install on Windows, every flag in the main command, and the common errors.

Why Not Export MP4 Straight From SFM?

SFM can write video files, but the options are dated. Its AVI export is uncompressed, so files grow very large. Animators on the Steam forums report corrupted AVI files once they pass 4 GB, and some say the AVI exporter fails outright.

The MP4 and MOV options depend on Apple QuickTime for Windows. Apple stopped supporting QuickTime for Windows in 2016, so installing it now is a security risk. Users also report shifted contrast and dull colors in SFM’s MP4 output.

An image sequence avoids all of this. Each frame is a separate file, so a crash at frame 900 leaves frames 0 to 899 safe. You can also re-encode without rendering again. Before exporting, check our best SFM render settings guide.

Step 1: Export an Image Sequence From SFM

Open your session and go to File > Export > Movie. In the export dialog, choose an image sequence instead of a movie file. SFM offers several still formats:

• TGA: SFM’s native format. It writes slightly faster, but files are large.
• PNG: lossless and widely supported. This is the best pick for most people.
• JPEG: lossy. Avoid it, because FFmpeg will compress the frames a second time.
• PFM: 32-bit float per channel for heavy color grading. Files are huge and few tools read them.

Use a short file name with no spaces, such as shot, and an empty output folder. Note the frame rate in the dialog. SFM sessions usually run at 24 fps, and FFmpeg must use the same number later.

Tick the option to export sound. SFM saves the audio as a WAV file next to the frames. Afterward, check the file names. You should see a padded counter like shot_0000.png, shot_0001.png and so on. Count the digits and note the first number, because both go into the FFmpeg command.

Framing and light decide how the final video looks, not the encoder. Our SFM camera tips and SFM lighting guide cover both.

Step 2: Install FFmpeg on Windows

FFmpeg.org only publishes source code. For Windows, its download page links to ready-made builds from gyan.dev and BtbN. Either works. The gyan.dev “release essentials” ZIP is small and includes libx264, libx265 and libvpx.

• Download the ZIP and extract it.
• Rename the extracted folder to ffmpeg and move it to C:\ffmpeg.
• Search Windows for “Edit the system environment variables” and open Environment Variables.
• Under your user variables, select Path, click Edit, then New, and add C:\ffmpeg\bin.
• Open a fresh Command Prompt window.

Type this and press Enter:

ffmpeg -version

A version number means FFmpeg is ready. “Not recognized” means the PATH entry is wrong or the window was opened too early.

Step 3: The FFmpeg Command to Render SFM to MP4

Open Command Prompt in your frames folder: type cmd in the File Explorer address bar and press Enter. Then run:

ffmpeg -framerate 24 -i shot_%04d.tga -i audio.wav -c:v libx264 -crf 18 -preset slow -pix_fmt yuv420p -c:a aac -b:a 192k -shortest output.mp4

Here is what each part does:

Flag	What it does
-framerate 24	Tells FFmpeg how fast to read the frames. Without it, the image reader assumes 25 fps.
-i shot_%04d.tga	The frame pattern. %04d means a four-digit, zero-padded number.
-i audio.wav	The second input: your SFM sound track.
-c:v libx264	Encodes video as H.264, the most compatible MP4 codec.
-crf 18	Constant quality. Lower means better quality and bigger files.
-preset slow	Spends more time to get a smaller file at the same quality.
-pix_fmt yuv420p	Uses 4:2:0 color, which every player and website supports.
-c:a aac -b:a 192k	Encodes audio to AAC at 192 kbps.
-shortest	Ends the file when the shorter input runs out.

Matching the Number Pattern

Match %04d to the digits in your file names. Five digits need %05d. FFmpeg looks for the first frame between 0 and 4. If your sequence starts higher, say at 120 because you exported part of a shot, add -start_number 120 before the -i for the frames.

-framerate vs -r

Put -framerate before the frame input to time the stills. A -r after the inputs sets the output rate, and FFmpeg drops or duplicates frames to hit it. Use -r only when you want a different output rate.

CRF and Preset: Picking Quality and File Size

The FFmpeg H.264 guide gives libx264 a CRF scale of 0 to 51. Zero is lossless, 23 is the default, and 51 is the worst. The guide calls 17 or 18 visually lossless or close to it. The scale is exponential: raising CRF by 6 roughly halves the file size, and lowering it by 6 roughly doubles it.

CRF	Quality	Relative file size	Good for
12	Near lossless	About 4x the CRF 24 size	Master copies for later editing
14 to 18	High, visually lossless	About 2x to 3x the CRF 24 size	YouTube uploads, portfolio pieces
20 to 23	Standard	About 1.1x to 1.6x	Sharing, Discord, previews
24 to 28	Visible softness	About 0.6x to 1x	Quick tests, drafts

Presets change speed, not the quality target. In order, they run ultrafast, superfast, veryfast, faster, fast, medium, slow, slower and veryslow. Medium is the default. For SFM work, slow is a good balance. You can also add -tune animation, which the x264 guide lists for animated content.

Smaller Files With H.265

Swap libx264 for libx265 to cut file size. The FFmpeg H.265 guide says its default CRF of 28 should look like x264 at CRF 23 at about half the size. Add -tag:v hvc1 so Apple players accept the file. Older PCs decode H.265 slowly, so keep an H.264 copy too.

ffmpeg -framerate 24 -i shot_%04d.png -i audio.wav -c:v libx265 -crf 22 -preset slow -pix_fmt yuv420p -tag:v hvc1 -c:a aac -b:a 192k -shortest output_hevc.mp4

YouTube-Ready Settings and Scaling

YouTube’s upload guide asks for MP4 with the moov atom at the front, H.264 High Profile, 4:2:0 chroma and AAC-LC audio at 48 kHz. Its suggested SDR bitrate at 24 to 30 fps is 8 Mbps for 1080p and 16 Mbps for 1440p.

ffmpeg -framerate 24 -i shot_%04d.png -i audio.wav -vf scale=1920:-2 -c:v libx264 -crf 18 -preset slow -profile:v high -pix_fmt yuv420p -c:a aac -b:a 192k -ar 48000 -movflags +faststart -shortest youtube.mp4

-vf scale=1920:-2 resizes the width to 1920 and picks an even height that keeps the aspect ratio. Use scale=2560:-2 for 1440p. -movflags +faststart moves the index to the start so playback begins before the file fully loads.

Fixing Audio Sync

Most sync problems come from a wrong -framerate. If SFM rendered at 30 fps and you read the frames at 24, the video runs 25 percent long and drifts away from the sound. If the audio needs a fixed nudge, put -itsoffset 0.5 before -i audio.wav to delay it by half a second.

GIF, WebM and Transparent Backgrounds

For a GIF, build a custom palette in the same pass for cleaner color:

ffmpeg -framerate 24 -i shot_%04d.png -vf "fps=15,scale=640:-1:flags=lanczos,split[a][b];[a]palettegen[p];[b][p]paletteuse" clip.gif

For WebM, use VP9 in constant quality mode. The FFmpeg VP9 guide says CRF runs from 0 to 63, with 15 to 35 the useful range, and -b:v 0 is required for true constant quality.

ffmpeg -framerate 24 -i shot_%04d.png -i audio.wav -c:v libvpx-vp9 -crf 30 -b:v 0 -c:a libopus -shortest clip.webm

SFM cannot render a transparent background on its own. The usual workaround is to light your subject against a flat green or blue backdrop, then key the color out. FFmpeg’s chromakey filter can do this, and the result can go to VP9 WebM with alpha or to ProRes 4444 for editors:

ffmpeg -framerate 24 -i shot_%04d.png -vf "chromakey=0x00FF00:0.12:0.05,format=yuva420p" -c:v libvpx-vp9 -crf 30 -b:v 0 alpha.webm

ffmpeg -framerate 24 -i shot_%04d.png -vf "chromakey=0x00FF00:0.12:0.05" -c:v prores_ks -profile:v 4444 -pix_fmt yuva444p10le alpha.mov

Adjust the similarity and blend numbers until edges look clean. ProRes 4444 files are huge, so use them as editing masters only.

A Reusable Batch File

Save the text below as render.bat in Notepad and drop it in your frames folder. Double-click it to encode. Inside a .bat file, every % in the pattern must be doubled, so %04d becomes %%04d.

@echo off
cd /d "%~dp0"
set FPS=24
set NAME=shot
ffmpeg -framerate %FPS% -i %NAME%_%%04d.png -i audio.wav -c:v libx264 -crf 18 -preset slow -pix_fmt yuv420p -c:a aac -b:a 192k -movflags +faststart -shortest %NAME%.mp4
pause

Troubleshooting SFM to MP4 Errors

Error or symptom	Likely cause	Fix
“No such file or directory” or “Could find no file with path”	Wrong name, digit count or start number	Check the real file names, match %04d, add -start_number
“height not divisible by 2”	Odd width or height with yuv420p	Add -vf scale=1920:-2 or scale=trunc(iw/2)*2:trunc(ih/2)*2
Washed-out or shifted colors	Color matrix or range mismatch	Add -vf scale=out_color_matrix=bt709:out_range=tv and -colorspace bt709 -color_primaries bt709 -color_trc bt709
Video stops early	A missing frame number in the sequence	Re-render or rename the missing frame; FFmpeg stops at the first gap
Audio drifts out of sync	Frame rate mismatch	Set -framerate to the SFM export rate
“ffmpeg is not recognized”	PATH not set	Add C:\ffmpeg\bin and reopen Command Prompt

Always check your frame count before you encode: a single missing number in the sequence makes FFmpeg stop at that point, and the MP4 simply ends early. Sort the folder by name and compare the last frame number with your shot length.

Missing textures are an SFM problem, not an FFmpeg one. Our guides to importing SFM models from the Steam Workshop and decompiling SFM models with Crowbar fix those.

Alternatives to FFmpeg

Prefer a timeline? Several free editors import image sequences directly:

• DaVinci Resolve: shows a numbered sequence as one clip in the Media Pool.
• Blender Video Sequencer: use Add > Image/Sequence and select all frames. Handy if you already use our Blender to SFM workflow.
• Shotcut: open the first frame and tick the image sequence option.
• HandBrake: does not open image sequences. Make an MP4 with FFmpeg first, then use HandBrake if you want to re-compress it.

Render SFM to MP4 FAQs