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To stream a prerecorded file to YouTube Live at a constant frame rate (CFR), have FFmpeg read it in real time, convert its frames to your chosen output cadence, encode the result, and send it to YouTube’s live ingest endpoint. For a 30-fps H.264 stream, the example below uses a 60-frame GOP for a two-second keyframe interval. Live-stream settings are not the same as settings for an ordinary YouTube upload.
How the live-file workflow works
FFmpeg reads the source file at playback speed, converts the video to a fixed output cadence by dropping or duplicating frames as needed, and encodes it for live ingest. YouTube receives that encoded stream through RTMP or RTMPS using the server URL and stream key shown in YouTube Studio.
This is a live broadcast of file playback, not a normal video upload. For uploads, YouTube says to encode and upload at the frame rate at which the content was recorded. For live ingest, choose a suitable output frame rate and follow the live encoder recommendations for codec, bitrate, and keyframes. See YouTube’s live encoder settings and YouTube’s upload encoding guidance.
Prepare the file and YouTube stream
- Check your FFmpeg build. The example uses
libx264; that encoder is available only in FFmpeg builds compiled with it. Runffmpeg -encodersand check thatlibx264appears in the list. - Set up the live stream in YouTube Studio. Create or open the live stream and copy the server URL and stream key YouTube provides. Keep the key private: anyone who has it may be able to send video to your stream.
- Choose output settings. Match the resolution and frame rate to your intended live presentation, and choose a bitrate your upstream connection can sustain continuously. The example targets 30 fps and uses 10 Mbps video, which YouTube lists as its recommended H.264 bitrate for 1080p30 live ingestion. That figure is a platform recommendation, not a guarantee your connection can maintain it.
- Choose whether playback should repeat. The command below loops the input indefinitely. Remove
-stream_loop -1if you want the broadcast to end when the file finishes.
FFmpeg command for a 30-fps live stream
ffmpeg -re -stream_loop -1 -i input.mp4
-vf "fps=30"
-c:v libx264 -preset veryfast -pix_fmt yuv420p
-b:v 10M -maxrate 10M -bufsize 20M
-g 60 -keyint_min 60 -sc_threshold 0
-c:a aac -b:a 128k -ar 44100
-f flv "rtmp://SERVER/STREAM_KEY"This is an adaptable starting point, not a tested command. Replace input.mp4 with your file and replace the endpoint placeholder with the server URL and stream key from YouTube Studio. Do not share or publish the key. YouTube supports RTMP/RTMPS live ingest and lists H.264, H.265/HEVC, and AV1 video codecs; this example uses H.264 as a broadly compatible profile.
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What the important options do
-rereads the file at its native playback speed, rather than sending it as fast as the machine can process it. That real-time pacing is appropriate for file playout as a live stream.-vf "fps=30"converts the output to 30 frames per second. FFmpeg drops or duplicates frames as needed to create that cadence.-g 60sets a 60-picture group of pictures. At 30 fps, that is a two-second keyframe interval.-keyint_min 60and-sc_threshold 0help keep the GOP cadence fixed instead of introducing shorter intervals at scene changes.-b:v 10Msets the target video bitrate.-maxrateand-bufsizeare rate-control parameters; they do not by themselves guarantee a constant instantaneous bitrate. YouTube recommends CBR for live RTMP/RTMPS, so use an appropriate encoder rate-control configuration and verify stream health rather than assuming these options guarantee CBR behavior.-c:a aac -b:a 128k -ar 44100encodes audio as AAC at 128 kbps and 44.1 kHz. Confirm the input has usable audio, or adapt the command if it does not.-f flvselects the FLV container commonly used for RTMP output.
Set frame rate and keyframe interval together
A GOP size is measured in frames, while the keyframe interval is experienced in seconds. YouTube recommends a two-second keyframe frequency and says not to exceed four seconds. Calculate GOP length as frame rate multiplied by interval: for a two-second interval, use 50 frames at 25 fps, 60 at 30 fps, or 120 at 60 fps. See FFmpeg’s all-options documentation for GOP and codec timing details.
For an encoded fixed-rate output, the codec time base should correspond to one frame’s duration, and timestamps should advance by one time-base unit per frame. In normal use, FFmpeg’s output frame-rate conversion handles the cadence; do not confuse it with changing how input timestamps are interpreted.
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Choose a sustainable bitrate and resolution
YouTube’s live recommendations vary by codec, resolution, and frame rate. For H.264, the live guidance lists 8 Mbps for 720p30, 10 Mbps for 1080p30, and 17 Mbps for 1080p60. These are recommendations from YouTube, not measurements of your internet connection. Leave upstream headroom for network variation and other household or office traffic; if the connection cannot sustain the chosen bitrate, reduce the bitrate or output resolution.
Do not copy the example’s 10 Mbps setting blindly for a different resolution or frame rate. Select the output profile first, then consult YouTube’s current live bitrate table for its recommended settings. A higher frame rate or resolution generally requires more sustained bandwidth.
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Common frame-rate mistakes
Using input -r as a CFR fix
Input -r has a different purpose from output frame-rate conversion: it ignores stored timestamps and generates new ones at the specified rate, and is intended for raw formats. Do not casually place input -r before an ordinary video file to fix variable frame rate. Use an encoding path with an output target such as -vf "fps=30" instead. FFmpeg documents the distinction in its main documentation.
Using stream copy
-c:v copy copies compressed video without decoding and re-encoding. It therefore cannot establish a new constant frame cadence for an arbitrary variable-frame-rate source. To create CFR output, convert and encode the video.
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Setting an output rate without changing the GOP
The correct GOP size depends on the chosen frame rate. Keeping -g 60 while changing from 30 fps to 60 fps changes the interval from two seconds to one. Recalculate the frame count from the desired interval whenever you change FPS.
Test and troubleshoot before going live
YouTube recommends testing with similar movement and audio before the event, then monitoring stream health during the broadcast. Its live streaming error messages page covers issues including frame rate and keyframe timing.
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- YouTube reports an unsupported or unexpected frame rate: confirm the command contains output conversion such as
-vf "fps=30", and check the output profile and stream health. Do not substitute input-ron a normal file. - YouTube reports a keyframe interval issue: check both the output FPS and GOP size. For a two-second interval, use 60 frames at 30 fps, 50 at 25 fps, or 120 at 60 fps.
- The stream buffers or drops frames: compare the configured video bitrate with YouTube’s recommendation for the selected codec, resolution, and FPS, then check whether the upstream connection can sustain it. Reduce bitrate or resolution if necessary.
- FFmpeg says the encoder is unavailable: install or use a build that includes
libx264, or select an encoder present in your build and configure it for the chosen live profile. - The stream does not appear in YouTube Studio: verify that the server URL and stream key are copied from the correct live event, and that the key has not been truncated or exposed. Avoid posting the key in logs or screenshots.
- Playback ends unexpectedly: use
-stream_loop -1if the file should repeat. Without it, FFmpeg reaches the end of the file and exits.
When you want a normal YouTube upload instead
For a finished video upload, create a file rather than sending output to the live ingest endpoint. Remove real-time input pacing, choose a file container such as MP4, and preserve the recording frame rate in line with YouTube’s upload guidance. -movflags +faststart may help progressive download for MP4 files. Upload recommendations and live-stream recommendations serve different destinations; do not treat the live command above as a universal upload recipe.
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