go-gst/gst/gstauto/app/pipeline_app_writer.go

package app

import (
	"errors"
	"fmt"
	"strings"

	"github.com/tinyzimmer/go-gst/gst"
	"github.com/tinyzimmer/go-gst/gst/app"
	"github.com/tinyzimmer/go-gst/gst/gstauto"
)

// PipelineWriterApp implements a WritePipeliner that configures gstreamer
// with an appsrc. The appsrc allows for more granular control over the data
// at the start of the pipeline.
type PipelineWriterApp struct {
	*gstauto.PipelineWriter

	appSrc *app.Source
}

// NewPipelineWriterAppFromString returns a new PipelineWriterApp populated from
// the given launch string. An appsrc is added to the start of the launch string and made
// available via the GetAppSource method.
func NewPipelineWriterAppFromString(launchStr string) (*PipelineWriterApp, error) {
	pipelineWriter, err := gstauto.NewPipelineWriterFromString(addAppSourceToStr(launchStr))
	if err != nil {
		return nil, err
	}

	appPipeline := &PipelineWriterApp{PipelineWriter: pipelineWriter}

	// Retrieve the sources in the pipeline, most of the time there is just one
	var sources []*gst.Element
	sources, err = pipelineWriter.Pipeline().GetSourceElements()
	if err != nil {
		runOrPrintErr(pipelineWriter.Pipeline().Destroy)
		return nil, err
	}

	// Fetch the appsrc and make a local reference to it
	for _, src := range sources {
		if strings.Contains(src.Name(), "appsrc") {
			appPipeline.appSrc = &app.Source{Element: src}
		}
	}

	// Return the pipeline
	return appPipeline, nil
}

// NewPipelineWriterAppFromConfig returns a new PipelineWriterApp populated from
// the given launch config. An appsrc is added to the start of the launch config and
// made available via the GetAppSource method.
func NewPipelineWriterAppFromConfig(cfg *gstauto.PipelineConfig) (*PipelineWriterApp, error) {
	if cfg.Elements == nil {
		return nil, errors.New("Elements cannot be nil in the config")
	}
	pipelineWriter, err := gstauto.NewPipelineWriter("")
	if err != nil {
		return nil, err
	}

	defer func() {
		if err != nil {
			runOrPrintErr(pipelineWriter.Pipeline().Destroy)
		}
	}()

	cfg.PushPluginToTop(&gstauto.PipelineElement{Name: "appsrc"})

	if err = cfg.Apply(pipelineWriter.Pipeline()); err != nil {
		return nil, err
	}

	appPipeline := &PipelineWriterApp{PipelineWriter: pipelineWriter}

	// Retrieve the sources in the pipeline, most of the time there is just one
	var sources []*gst.Element
	sources, err = pipelineWriter.Pipeline().GetSourceElements()
	if err != nil {
		return nil, err
	}

	// Fetch the appsrc and make a local reference to it
	for _, src := range sources {
		if strings.Contains(src.Name(), "appsrc") {
			appPipeline.appSrc = &app.Source{Element: src}
		}
	}

	return appPipeline, nil
}

func addAppSourceToStr(pstr string) string {
	if pstr == "" {
		return "appsrc"
	}
	return fmt.Sprintf("%s ! appsrc", pstr)
}

// GetAppSource returns the app src for this pipeline.
func (p *PipelineWriterApp) GetAppSource() *app.Source { return p.appSrc }