You can stream a 4K prerecorded video to YouTube Live at 1080p without first converting the file: play the 4K file in streaming software and set the software’s output resolution to 1920×1080. YouTube receives the 1080p stream; your original file can stay 4K.
What downscaling changes—and what it does not
Downscaling changes the resolution sent by your streaming software, not the resolution of the source file. A 4K video remains 4K on disk while the software scales its picture to 1920×1080 for YouTube’s live ingest. YouTube then transcodes the incoming live stream into formats for viewers. In YouTube Live Control Room, set the encoder details to match the outgoing stream, not the source file. YouTube’s live encoder guidance covers the required resolution, frame rate and bitrate.
For a documentary, choose a frame rate that suits the footage and your available upload bandwidth. A 30 fps output is a sensible match for 30 fps source material; use 60 fps when the source and intended motion cadence warrant it. YouTube’s recommended bitrate is higher at 60 fps.
Set up the 1080p output in OBS
- Add the video: In OBS, add a Media Source and select the prerecorded file. Enable the source’s restart behavior if you want playback to begin again when it reaches the end. Exact labels can vary by OBS version.
- Check framing: Make sure the source fits the canvas. For a 16:9 4K file, scaling to 1920×1080 preserves the aspect ratio. If the source has a different shape, decide whether to crop the sides or letterbox it; avoid stretching the image.
- Set the output size: Open Settings > Video. Keep Base (Canvas) Resolution appropriate for the composition, and set Output (Scaled) Resolution to 1920×1080. Choose a downscale filter and inspect the picture at fine detail and during motion.
- Choose the frame rate: In the same Video settings, set Common FPS to 30 or 60 to match the source and desired cadence. Avoid converting a 30 fps documentary to 60 fps simply because the higher number is available.
- Configure streaming output: In Settings > Output, use an encoder and codec supported by your setup. Set rate control to CBR, the bitrate according to the table below, and keyframe interval to 2 seconds. In Settings > Stream, select YouTube and connect your account or enter the stream key from YouTube Live Control Room.
- Route and check audio: Confirm the Media Source’s audio is present in the OBS mixer, is not muted, and stays synchronized with the picture. Use stereo AAC or MP3; YouTube’s advanced recommendations list 128 Kbps and 44.1 kHz stereo.
- Run a private or unlisted test: Start a test stream before the intended broadcast. Check framing, motion, audio levels, synchronization and playback through the file’s end. In Live Control Room, verify stream health and read any warnings before sharing the broadcast.
Use YouTube’s 1080p bitrate recommendations
YouTube Help’s live encoder guidance, accessed October 3, 2026, gives these recommended ingestion bitrates. The minimums are lower bounds, not the recommended targets. Leave upload headroom so other network use does not destabilize the stream.
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| Output | Codec | Recommended bitrate | Listed minimum |
|---|---|---|---|
| 1080p, 30 fps | H.264 | 14 Mbps | 5 Mbps |
| 1080p, 30 fps | AV1 or H.265 (HEVC) | 10 Mbps | 4 Mbps |
| 1080p, 60 fps | H.264 | 17 Mbps | 6 Mbps |
| 1080p, 60 fps | AV1 or H.265 (HEVC) | 12 Mbps | 4 Mbps |
Use a codec your chosen encoder and streaming workflow support; YouTube’s support for a codec does not establish that every third-party encoder supports every combination. YouTube supports H.264, H.265 and AV1, recommends constant bitrate (CBR), and recommends a two-second keyframe frequency—do not exceed four seconds. It recommends RTMPS, the encrypted extension of RTMP. For SDR, use Rec. 709 and 8-bit depth. YouTube lists AAC or MP3 for audio, with 128 Kbps and 44.1 kHz stereo in its advanced recommendations. See YouTube’s encoder settings and bitrate table.
Choose a downscale filter and encoder that your computer can handle
OBS-related performance guidance describes bilinear as the least resource-intensive filter and Lanczos as more demanding but potentially sharper; bicubic is another option. These are trade-offs, not a universal quality ranking for every documentary. Compare fine detail, text and moving scenes using the actual video, then keep the filter that looks acceptable without overloading your machine. The scaling and performance guidance is hosted on a GitHub Wiki mirror; menu labels and options may vary by OBS version.
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Downscaling can reduce encoding work, and a lower frame rate means fewer frames to process. Hardware encoders such as Intel Quick Sync, AMD AMF and NVIDIA NVENC can reduce CPU load; OBS-related guidance notes there may be a quality trade-off at a given bitrate compared with x264. Test on your own system rather than assuming a particular encoder or filter will perform best.
Test the actual program before going live
A still frame cannot reveal every problem. YouTube advises testing with audio and movement similar to the planned stream and monitoring stream health and messages during the event. For prerecorded playback, also confirm that the file starts at the intended point, reaches its end as expected, and stays synchronized with its audio. YouTube’s instructions are in Choose live encoder settings, bitrates, and resolutions.
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- Confirm Live Control Room reports the intended 1920×1080 resolution and frame rate.
- Watch a moving scene for softness, judder, cropping or unexpected black bars.
- Listen for clipping, missing channels, silence or audio that drifts out of sync.
- Check stream health and resolve warnings before the audience arrives.
Troubleshoot common downscaling and live-stream problems
| Symptom | Likely cause | What to check |
|---|---|---|
| YouTube receives a resolution other than 1080p | The software’s scaled output or the selected streaming scene is not set to 1920×1080. | Recheck OBS Settings > Video and confirm the active output is 1920×1080; verify the stream details in Live Control Room. |
| Picture looks stretched or cropped | The source aspect ratio does not match the canvas, or the source was resized without preserving its shape. | Fit the source proportionally, then choose deliberate cropping or letterboxing for non-16:9 footage. |
| Stream health reports instability | The upload connection may not sustain the selected bitrate, or the computer may be overloaded. | Run an upload speed test, check for competing network traffic, and inspect OBS performance. If needed, use a lower frame rate or a supported hardware encoder, then test again. |
| Motion looks uneven | Output frame rate may not suit the source cadence, or the computer is dropping frames. | Match output FPS to the source where practical and monitor dropped frames and system load. |
| Audio is absent or out of sync | The media source audio may not be routed into the stream, may be muted, or may not remain synchronized during playback. | Check the OBS mixer and source audio settings, then test the full playback path before broadcasting. |
| Broadcast stops when the file ends | Playback reached the end without restarting or another source taking over. | For a one-time program, plan the end of the broadcast. For continuous playback, configure the Media Source to restart or build a playlist, then test the transition. |
| Stream key is rejected or the stream will not connect | The key or ingest configuration may not match the selected YouTube stream. | Check the current stream key and YouTube connection in Live Control Room and OBS; avoid publishing or sharing the key. |
Copyright and YouTube policy still apply
Downscaling does not change the rights attached to a documentary’s video, soundtrack, photographs, archive footage or other material. Before streaming, make sure you have the necessary rights or permission for the live use, including music and clips. YouTube’s copyright and monetization decisions are separate from whether the encoder settings are technically correct. A successful stream test is not a determination that the content complies with YouTube’s policies.
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