# Stream videos with on-demand encoding Robot: `/video/ondemand` 🤖/video/ondemand generates HTTP Live Streaming (HLS) playlists and segments on-demand for adaptive and cost-efficient playback. Stage: beta ## Usage example Enable streaming of a video stored on S3 in three variants (480p, 720p, 1080p) with on-demand encoding: ```json { "steps": { "import": { "robot": "/s3/import", "path": "${fields.input}", "credentials": "YOUR_AWS_CREDENTIALS", "return_file_stubs": true }, "vod": { "robot": "/video/ondemand", "use": "import", "variants": { "480p": { "preset": "hls/480p", "ffmpeg_stack": "{{ stacks.ffmpeg.recommended_version }}" }, "720p": { "preset": "hls/720p", "ffmpeg_stack": "{{ stacks.ffmpeg.recommended_version }}" }, "1080p": { "preset": "hls/1080p", "ffmpeg_stack": "{{ stacks.ffmpeg.recommended_version }}" } } }, "serve": { "use": "vod", "robot": "/file/serve" } } } ``` ## Parameters * `interpolate`: Controls whether Assembly Variables are interpolated for individual instruction fields. By default, most Robot instruction fields interpolate Assembly Variables. Set this to `false` to treat every instruction field as literal text, or set an individual field path to `false` to treat only that field as literal text. For Robot-specific fields that are literal by default, set this to `true` or set that field path to `true` to opt back into interpolation. Use field names such as `path`, or dotted paths such as `ffmpeg.vf` for nested objects. * `output_meta`: Allows you to specify a set of metadata that is more expensive on CPU power to calculate, and thus is disabled by default to keep your Assemblies processing fast. For images, you can add `"has_transparency": true` in this object to extract if the image contains transparent parts and `"dominant_colors": true` to extract an array of hexadecimal color codes from the image. For images, you can also add `"blurhash": true` to extract a [BlurHash](https://blurha.sh) string — a compact representation of a placeholder for the image, useful for showing a blurred preview while the full image loads. For videos, you can add the `"colorspace": true` parameter to extract the colorspace of the output video. For videos, you can also add `"interlaced": true` to detect whether the video is interlaced. This combines the cheap ffprobe `field_order` flag with a bounded `idet` sampling pass over the first frames of the source, exposing `interlaced`, `field_order`, and a diagnostic `interlace_detection` object under `file.meta`. This is computationally expensive and billed accordingly. For audio, you can add `"mean_volume": true` to get a single value representing the mean average volume of the audio file. You can also set this to `false` to skip metadata extraction and speed up transcoding. * `user_meta`: Adds custom metadata to each file emitted by this Robot without modifying the file’s contents. The values are merged with any existing `user_meta` carried by the input file. If both objects contain the same key, this Robot’s value takes precedence. Assembly Variables are supported, for example `{ "internal_file_id": "${file.id}" }`. * `result`: Whether the results of this Step should be present in the Assembly Status JSON * `queue`: Setting the queue to 'batch', manually downgrades the priority of jobs for this step to avoid consuming Priority job slots for jobs that don't need zero queue waiting times * `force_accept`: Force a Robot to accept a file type it would have ignored. By default, Robots ignore files they are not familiar with. [🤖/video/encode](/docs/robots/video-encode.md), for example, will happily ignore input images. With the `force_accept` parameter set to `true`, you can force Robots to accept all files thrown at them. This will typically lead to errors and should only be used for debugging or combatting edge cases. * `ignore_errors`: Ignore errors during specific phases of processing. Setting this to `["meta"]` will cause the Robot to ignore errors during metadata extraction. Setting this to `["execute"]` will cause the Robot to ignore errors during the main execution phase. Setting this to `true` is equivalent to `["meta", "execute"]` and will ignore errors in both phases. * `use`: Specifies which Step(s) to use as input. * You can pick any names for Steps except `":original"` (reserved for user uploads handled by Transloadit) * You can provide several Steps as input with arrays: ```json { "use": [ ":original", "encoded", "resized" ] } ``` * You can also tag input Steps with `as` to pass semantic intent to robots: ```json { "use": [ { "name": ":original", "as": "image" }, { "name": ":original", "as": "mask" } ] } ``` > [!Tip] > That's likely all you need to know about `use`, but you can view [Advanced use cases](/docs/topics/use-parameter.md). * `variants`: Defines the variants the video player can choose from. The keys are the names of the variant as they will appear in the generated playlists and URLs. * `enabled_variants`: Specifies which variants, defined in the variants parameter, are enabled. Non-enabled variants will not be included in the multivariant playlist. * `segment_duration`: The duration of each segment in seconds. * `sign_urls_for`: When signing URLs is enabled, the URLs in the generated playlist files will be signed. This parameter specifies the duration (in seconds) that the signed URLs will remain valid. Use the modern `sig` + `exp` format for new integrations. Legacy `s` signatures are deprecated. Shorter expirations reduce the replay window, but they also reduce cache reuse and can increase segment re-generation and latency. * `asset`: Controls which file is generated. For example, if the parameter is unset, a multivariant playlist referencing the variants is generated. * `asset_param_name`: Specifies from which URL parameter the asset parameter value is taken and which URL parameter to use when generating playlist files.