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_debug_test.go

@@ -0,0 +1,113 @@
+package rtp
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"testing"
+
+	"github.com/pion/rtp"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRTPPayloadReaderDebug(t *testing.T) {
+	// 创建简单的测试数据
+	originalData := []byte("Hello World")
+
+	// 生成RTP包
+	packets := generateRTPPacketsForDebug(originalData, 0, 1000)
+
+	fmt.Printf("Generated %d RTP packets\n", len(packets))
+	for i, packet := range packets {
+		fmt.Printf("Packet %d: Seq=%d, Payload=%s, PayloadLen=%d\n", i, packet.SequenceNumber, string(packet.Payload), len(packet.Payload))
+	}
+
+	// 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)
+		fmt.Printf("Marshaled packet length: %d\n", len(data))
+
+		// 写入RTP包长度和数据
+		buf.Write([]byte{byte(len(data) >> 8), byte(len(data))})
+		buf.Write(data)
+	}
+
+	fmt.Printf("Buffer size: %d\n", buf.Len())
+	fmt.Printf("Original data length: %d\n", len(originalData))
+	fmt.Printf("Original data: %s\n", string(originalData))
+
+	// 使用RTPPayloadReader读取数据
+	reader := NewRTPPayloadReader(NewRTPTCPReader(&buf))
+
+	// 逐步读取数据
+	allData := make([]byte, 0)
+	bufSize := 3
+
+	for len(allData) < len(originalData) {
+		result := make([]byte, bufSize)
+		fmt.Printf("Buffer length before read: %d\n", reader.buffer.Length)
+		fmt.Printf("Buffer count before read: %d\n", reader.buffer.Count())
+		n, err := reader.Read(result)
+		fmt.Printf("Read returned: n=%d, err=%v\n", n, err)
+		fmt.Printf("Read data: %s\n", string(result[:n]))
+		fmt.Printf("Buffer length after read: %d\n", reader.buffer.Length)
+		fmt.Printf("Buffer count after read: %d\n", reader.buffer.Count())
+
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			assert.NoError(t, err)
+		}
+		if n == 0 {
+			break
+		}
+		allData = append(allData, result[:n]...)
+		fmt.Printf("All data so far: %s\n", string(allData))
+	}
+
+	fmt.Printf("Final data length: %d\n", len(allData))
+	fmt.Printf("Final data: %s\n", string(allData))
+
+	// 验证数据是否匹配
+	assert.Equal(t, originalData, allData)
+}
+
+func generateRTPPacketsForDebug(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
+}