# gst-validate-transcoding

`gst-validate-transcoding` is tool to create media files transcoding pipelines running inside the GstValidate monitoring infrastructure.

You can for example transcode any media file to Vorbis audio + VP8 video in a WebM container by doing:

    gst-validate-transcoding-GST_API_VERSION file:///./file.ogg file:///.../transcoded.webm -o 'video/webm:video/x-vp8:audio/x-vorbis'

`gst-validate-transcoding` will list every issue encountered during the execution of the transcoding operation in a human readable report like the one below:

    issue : buffer is out of the segment range Detected on theoradec0.srcpad
    at 0:00:00.096556426 Details : buffer is out of segment and shouldn't be
    pushed. Timestamp: 0:00:25.000 - duration: 0:00:00.040 Range:
    0:00:00.000 - 0:00:04.520 Description : buffer being pushed is out of
    the current segment's start-stop range. Meaning it is going to be
    discarded downstream without any use

The return code of the process will be 18 in case a `CRITICAL` issue has been found.

## The encoding profile serialization format

This is the serialization format of a GstEncodingProfile.

Internally the transcoding application uses GstEncodeBin. `gst-validate-transcoding-GST_API_VERSION` uses its own serialization format to describe the `GstEncodeBin.profile` property of the encodebin.

The simplest serialized profile looks like:

    muxer_source_caps:videoencoder_source_caps:audioencoder_source_caps

For example to encode a stream into a WebM container, with an OGG audio stream and a VP8 video stream, the serialized GstEncodingProfile will look like:

    video/webm:video/x-vp8:audio/x-vorbis

You can also set the preset name of the encoding profile using the caps+preset_name syntax as in:

    video/webm:video/x-vp8+youtube-preset:audio/x-vorbis

Moreover, you can set the presence property of an encoding profile using the `|presence` syntax as in:

    video/webm:video/x-vp8|1:audio/x-vorbis

This field allows you to specify how many times maximum a GstEncodingProfile can be used inside an encodebin.

You can also use the `restriction_caps->encoded_format_caps` syntax to specify the restriction caps to be set on a GstEncodingProfile. It corresponds to the restriction GstCaps to apply before the encoder that will be used in the profile. The fields present in restriction caps are properties of the raw stream (that is, before encoding), such as height and width for video and depth and sampling rate for audio. This property does not make sense for muxers.

To force a video stream to be encoded with a Full HD resolution (using WebM as the container format, VP8 as the video codec and Vorbis as the audio codec), you should use:

    video/webm:video/x-raw,width=1920,height=1080->video/x-vp8:audio/x-vorbis

### Some serialized encoding formats examples:

MP3 audio and H264 in MP4:

    video/quicktime,variant=iso:video/x-h264:audio/mpeg,mpegversion=1,layer=3

Vorbis and theora in OGG:

    application/ogg:video/x-theora:audio/x-vorbis

AC3 and H264 in MPEG-TS:

    video/mpegts:video/x-h264:audio/x-ac3

# Invocation

`gst-validate-transcoding` takes and input URI and an output URI, plus a few options to control how transcoding should be tested.

## Options

- `--set-scenario`: Let you set a scenario, it can be a full path to a scenario file or the name of the scenario (name of the file without the `.scenario` extension).
- `-l`, `--list-scenarios`: List the available scenarios that can be run.
- `--scenarios-defs-output-file`: The output file to store scenarios details. Implies `--list-scenario`.
- `-t`, `--inspect-action-type`: Inspect the available action types with which to write scenarios if no parameter passed, it will list all available action types otherwize will print the full description of the wanted types.
- `--set-configs`: Let you set a config scenario. The scenario needs to be set as `config`. You can specify a list of scenarios separated by `:`. It will override the GST_VALIDATE_SCENARIO environment variable.
- `-e`, `--eos-on-shutdown`: If an EOS event should be sent to the pipeline if an interrupt is received, instead of forcing the pipeline to stop. Sending an EOS will allow the transcoding to finish the files properly before exiting.
- `-r`, `--force-reencoding`: Whether to try to force reencoding, meaning trying to only remux if possible, defaults to `TRUE`.

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