refactor: frame converter and mp4 track improvements

- Refactor frame converter implementation
- Update mp4 track to use ICodex
- General refactoring and code improvements

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

plugin/rtp/pkg/reader_test.go

@@ -0,0 +1,153 @@
+package rtp
+
+import (
+	"bytes"
+	"io"
+	"testing"
+
+	"github.com/pion/rtp"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRTPPayloadReader(t *testing.T) {
+	// 创建测试数据
+	originalData := []byte("Hello, World! This is a test payload for RTP packets.")
+
+	// 生成RTP包
+	packets := generateRTPPackets(originalData, 0, 1000)
+
+	// 将RTP包序列化到缓冲区
+	var buf bytes.Buffer
+	for _, packet := range packets {
+		data, err := packet.Marshal()
+		assert.NoError(t, err)
+
+		// 写入RTP包长度和数据
+		buf.Write([]byte{byte(len(data) >> 8), byte(len(data))})
+		buf.Write(data)
+	}
+
+	// 使用RTPPayloadReader读取数据
+	reader := NewRTPPayloadReader(NewRTPTCPReader(&buf))
+
+	// 读取所有数据
+	result := make([]byte, len(originalData))
+	n, err := reader.Read(result)
+	assert.NoError(t, err)
+	assert.Equal(t, len(originalData), n)
+
+	// 验证数据是否匹配
+	assert.Equal(t, originalData, result)
+}
+
+func TestRTPPayloadReaderWithBuffer(t *testing.T) {
+	// 创建测试数据
+	originalData := []byte("This is a longer test payload that will be split across multiple RTP packets to test the buffering functionality of the RTPPayloadReader.")
+
+	// 生成RTP包
+	packets := generateRTPPackets(originalData, 0, 2000)
+
+	// 将RTP包序列化到缓冲区
+	var buf bytes.Buffer
+	for _, packet := range packets {
+		data, err := packet.Marshal()
+		assert.NoError(t, err)
+
+		// 写入RTP包长度和数据
+		buf.Write([]byte{byte(len(data) >> 8), byte(len(data))})
+		buf.Write(data)
+	}
+
+	// 使用RTPPayloadReader读取数据
+	reader := NewRTPPayloadReader(NewRTPTCPReader(&buf))
+
+	// 使用较小的缓冲区读取数据
+	allData := make([]byte, 0)
+	bufSize := 10
+
+	for len(allData) < len(originalData) {
+		result := make([]byte, bufSize)
+		n, err := reader.Read(result)
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			assert.NoError(t, err)
+		}
+		if n == 0 {
+			break
+		}
+		allData = append(allData, result[:n]...)
+	}
+
+	// 验证数据是否匹配
+	assert.Equal(t, originalData, allData)
+}
+
+func TestRTPPayloadReaderSimple(t *testing.T) {
+	// 创建简单的测试数据
+	originalData := []byte("Hello World")
+
+	// 生成RTP包
+	packets := generateRTPPackets(originalData, 0, 1000)
+
+	// 将RTP包序列化到缓冲区
+	var buf bytes.Buffer
+	for _, packet := range packets {
+		data, err := packet.Marshal()
+		assert.NoError(t, err)
+
+		// 写入RTP包长度和数据
+		buf.Write([]byte{byte(len(data) >> 8), byte(len(data))})
+		buf.Write(data)
+	}
+
+	// 使用RTPPayloadReader读取数据
+	reader := NewRTPPayloadReader(NewRTPTCPReader(&buf))
+
+	// 读取所有数据
+	result := make([]byte, len(originalData))
+	n, err := reader.Read(result)
+	assert.NoError(t, err)
+	assert.Equal(t, len(originalData), n)
+
+	// 验证数据是否匹配
+	assert.Equal(t, originalData, result)
+}
+
+func generateRTPPackets(data []byte, ssrc uint32, initialSeq uint16) []*rtp.Packet {
+	var packets []*rtp.Packet
+	seq := initialSeq
+	maxPayloadSize := 100
+
+	for len(data) > 0 {
+		// 确定当前包的负载大小
+		payloadSize := maxPayloadSize
+		if len(data) < payloadSize {
+			payloadSize = len(data)
+		}
+
+		// 创建RTP包
+		packet := &rtp.Packet{
+			Header: rtp.Header{
+				Version:        2,
+				Padding:        false,
+				Extension:      false,
+				Marker:         false,
+				PayloadType:    96,
+				SequenceNumber: seq,
+				Timestamp:      123456,
+				SSRC:           ssrc,
+			},
+			Payload: data[:payloadSize],
+		}
+
+		packets = append(packets, packet)
+
+		// 更新数据和序列号
+		data = data[payloadSize:]
+		seq++
+	}
+
+	return packets
+}