Redesign codec

Resolves https://github.com/pion/mediadevices/issues/114

* Remove codec registrar
* Completely redesign how codec is being discovered, tuned, and built
* Update examples
* Update unit tests

pkg/codec/vaapi/params.go

@@ -1,7 +1,17 @@
 package vaapi
 
+import (
+	"io"
+
+	"github.com/pion/mediadevices/pkg/codec"
+	"github.com/pion/mediadevices/pkg/io/video"
+	"github.com/pion/mediadevices/pkg/prop"
+	"github.com/pion/webrtc/v2"
+)
+
 // ParamVP8 stores VP8 encoding parameters.
 type ParamVP8 struct {
+	codec.BaseParams
 	Sequence        SequenceParamVP8
 	RateControlMode RateControlMode
 	RateControl     RateControlParam
@@ -14,8 +24,38 @@ type SequenceParamVP8 struct {
 	ClampQindexLow  uint
 }
 
+// NewVP8Param returns default parameters of VP8 codec.
+func NewVP8Param() (ParamVP8, error) {
+	return ParamVP8{
+		Sequence: SequenceParamVP8{
+			ClampQindexLow:  9,
+			ClampQindexHigh: 127,
+		},
+		RateControlMode: RateControlVBR,
+		RateControl: RateControlParam{
+			BitsPerSecond:    400000,
+			TargetPercentage: 80,
+			WindowSize:       1500,
+			InitialQP:        60,
+			MinQP:            9,
+			MaxQP:            127,
+		},
+	}, nil
+}
+
+// Name represents the codec name
+func (p *ParamVP8) Name() string {
+	return webrtc.VP8
+}
+
+// BuildVideoEncoder builds VP8 encoder with given params
+func (p *ParamVP8) BuildVideoEncoder(r video.Reader, property prop.Media) (io.ReadCloser, error) {
+	return newVP8Encoder(r, property, *p)
+}
+
 // ParamVP9 represents VAEncSequenceParameterBufferVP9 and other parameter buffers.
 type ParamVP9 struct {
+	codec.BaseParams
 	RateControlMode RateControlMode
 	RateControl     RateControlParam
 }
@@ -52,3 +92,28 @@ const (
 	RateControlQVBR           RateControlMode = 0x00000400
 	RateControlAVBR           RateControlMode = 0x00000800
 )
+
+// NewVP9Param returns default parameters of VP9 codec.
+func NewVP9Param() (ParamVP9, error) {
+	return ParamVP9{
+		RateControlMode: RateControlVBR,
+		RateControl: RateControlParam{
+			BitsPerSecond:    400000,
+			TargetPercentage: 80,
+			WindowSize:       1500,
+			InitialQP:        60,
+			MinQP:            9,
+			MaxQP:            127,
+		},
+	}, nil
+}
+
+// Name represents the codec name
+func (p *ParamVP9) Name() string {
+	return webrtc.VP9
+}
+
+// BuildVideoEncoder builds VP9 encoder with given params
+func (p *ParamVP9) BuildVideoEncoder(r video.Reader, property prop.Media) (io.ReadCloser, error) {
+	return newVP9Encoder(r, property, *p)
+}