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Ultimate Guide: 4K SDI/HDMI to MP4 with Hardware Encoding

Our new developer guide shows how to record any LT-300 series input to H.264 or HEVC MP4 files on NVIDIA, Intel or AMD GPUs, split long recordings automatically and record several inputs at once.

Technology 2 min read #LT-300
Ultimate Guide: 4K SDI/HDMI to MP4 with Hardware Encoding

Recording is the first thing most people do with an LT-300 series card.

Additionally, the most common question we hear is how to do it well.

It asks which encoder, which bitrate, and what happens after eight hours.

Our new developer guide answers all of it, step by step.

In about 20 minutes, you go from your first MP4 file to long, multi-input recordings started from your own code.

They are encoded on the GPU by NVIDIA NVENC, Intel Quick Sync, or AMD AMF.

What the guide covers

  • Your first MP4:record any SDI or HDMI input at its own resolution and frame rate with one command.
  • The right hardware encoder:H.264 or HEVC on an NVIDIA, Intel or AMD GPU, with the preset and keyframe interval you need.
  • Bitrate or quality:constant bitrate for predictable file sizes, or constant quality for a steady image.
  • Long recordings:files split automatically by duration or by size, each with its own timestamped name.
  • Several inputs at once:every input records in parallel, and MP4 files carry audio and video together.
  • Recording from your own code:the same settings in a JSON request, with status polling and stop, pause and start commands.

One command to start

With the curl command line tool, a recording starts with a single line. It runs until you press Ctrl+C.

$ ecurl rec lt300:/0/hdmi-in/0/file -d media=video/mp4

Add the encoder settings to record 4K in HEVC on an NVIDIA GPU at a constant 20 Mbps. Include the recording of 4K in HEVC with an NVIDIA GPU at a fixed 20 Mbps.

$ ecurl rec lt300:/0/sdi-in/0/file \
-d media=video/mp4 \
-d extra.hw=nvenc \
-d extra.codec=hevc \
-d extra.bitrate=20000000

Change extra.hw to qsv for Intel Quick Sync or amf for AMD. HEVC gives smaller files than H.264 at the same quality.

Eight hours, in ten-minute files

Long sessions in surgery, inspection or monitoring should not end up as one huge file.

Additionally, set a total duration and a split interval.

The card’s agent starts a new file every ten minutes, without overwriting anything.

$ ecurl rec lt300:/0/sdi-in/0/file \
-d media=video/mp4 \
-d location=/data/videos \
-d duration=28800 \
-d splitDuration=600

The guide also shows how to split by size instead. Additionally, it explains how to record the four SDI inputs of an LT311 in parallel. It also covers what to check when it does not start.

Who it is for

The guide is written for developers and integrators using LT311, LT312, or LT313 card.

Additionally, every example works from the command line first, so you can test a setting quickly before your app.

Read the recording guide
All developer resources

Building a recording product and not sure which card, codec or GPU to choose? Talk to our engineers: we help you size the system for your number of inputs and resolution.

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