我知道可以使用Wireshark和VLC保存RTP h264流。但为了更多地了解视频流，我正试着自己做。关于这个话题，有几个相关的问题可以很好地阅读:
如何处理原始UDP数据包，以便它们可以被directshow源过滤器中的解码器过滤器解码
使用ffmpeg (libavcodec)解码RTP上的H264视频的问题
如何将H.264 UDP数据包转换为可播放的媒体流或文件(碎片整理)
以这些为背景，这是我目前的位置:
- 我可以通过UTP接收RTP数据包。
- 我按照上面的问题来解析数据包。
- 我将数据包写入一个文件，以x000001分隔，并根据上述指南再次添加NAL字节。
- 在文件的开头，我把SPS和PPS，我从我的代码的RTSP会话与服务器(再次由正确的字节分隔)。
我最终得到了一个据说有很多NAL帧的文件。然后我尝试在。264文件上运行ffmpeg以创建。mp4文件。这会产生几个错误:
[h264 @ 0x15257a0] decode_slice_header error
[h264 @ 0x15257a0]没有帧!
[h264 @ 0x15257a0]不存在的PPS引用
[h264 @ 0x15257a0]不存在的PPS 0引用
[buffer @ 0x15e16a0]无效的像素格式字符串'-1'
在我能解决这个问题之前，我基本上处于停顿状态。我已经彻底阅读了我上面链接到的问题，并且流绝对是可见的，因为我可以通过VLC连接和观看它，并且根据wireshark，传入的数据包绝对是H264 RTP数据包。如果VLC能做到，为什么我不能!我将非常感谢任何对我的错误的深入了解，并可能总结三个相互关联的问题，以解决它们之间的分歧。查看如何处理原始UDP数据包，以便它们可以被directshow源过滤器中的解码器过滤器解码
它有你需要的答案，但过程是这样的:
//Determine if the forbidden bit is set and the type of nal from the first byte
byte firstByte = packetData[offset];
//bool forbiddenZeroBit = ((firstByte & 0x80) >> 7) != 0;
byte nalUnitType = (byte)(firstByte & Common.Binary.FiveBitMaxValue);
//o The F bit MUST be cleared if all F bits of the aggregated NAL units are zero; otherwise, it MUST be set.
//if (forbiddenZeroBit && nalUnitType <= 23 && nalUnitType > 29) throw new InvalidOperationException("Forbidden Zero Bit is Set.");
//Determine what to do
switch (nalUnitType)
{
//Reserved - Ignore
case 0:
case 30:
case 31:
{
return;
}
case 24: //STAP - A
case 25: //STAP - B
case 26: //MTAP - 16
case 27: //MTAP - 24
{
//Move to Nal Data
++offset;
//Todo Determine if need to Order by DON first.
//EAT DON for ALL BUT STAP - A
if (nalUnitType != 24) offset += 2;
//Consume the rest of the data from the packet
while (offset < count)
{
//Determine the nal unit size which does not include the nal header
int tmp_nal_size = Common.Binary.Read16(packetData, offset, BitConverter.IsLittleEndian);
offset += 2;
//If the nal had data then write it
if (tmp_nal_size > 0)
{
//For DOND and TSOFFSET
switch (nalUnitType)
{
case 25:// MTAP - 16
{
//SKIP DOND and TSOFFSET
offset += 3;
goto default;
}
case 26:// MTAP - 24
{
//SKIP DOND and TSOFFSET
offset += 4;
goto default;
}
default:
{
//Read the nal header but don't move the offset
byte nalHeader = (byte)(packetData[offset] & Common.Binary.FiveBitMaxValue);
if (nalHeader > 5)
{
if (nalHeader == 6)
{
Buffer.WriteByte(0);
containsSei = true;
}
else if (nalHeader == 7)
{
Buffer.WriteByte(0);
containsPps = true;
}
else if (nalHeader == 8)
{
Buffer.WriteByte(0);
containsSps = true;
}
}
if (nalHeader == 1) containsSlice = true;
if (nalHeader == 5) isIdr = true;
//Done reading
break;
}
}
//Write the start code
Buffer.Write(NalStart, 0, 3);
//Write the nal header and data
Buffer.Write(packetData, offset, tmp_nal_size);
//Move the offset past the nal
offset += tmp_nal_size;
}
}
return;
}
case 28: //FU - A
case 29: //FU - B
{
/*
Informative note: When an FU-A occurs in interleaved mode, it
always follows an FU-B, which sets its DON.
* Informative note: If a transmitter wants to encapsulate a single
NAL unit per packet and transmit packets out of their decoding
order, STAP-B packet type can be used.
*/
//Need 2 bytes
if (count > 2)
{
//Read the Header
byte FUHeader = packetData[++offset];
bool Start = ((FUHeader & 0x80) >> 7) > 0;
//bool End = ((FUHeader & 0x40) >> 6) > 0;
//bool Receiver = (FUHeader & 0x20) != 0;
//if (Receiver) throw new InvalidOperationException("Receiver Bit Set");
//Move to data
++offset;
//Todo Determine if need to Order by DON first.
//DON Present in FU - B
if (nalUnitType == 29) offset += 2;
//Determine the fragment size
int fragment_size = count - offset;
//If the size was valid
if (fragment_size > 0)
{
//If the start bit was set
if (Start)
{
//Reconstruct the nal header
//Use the first 3 bits of the first byte and last 5 bites of the FU Header
byte nalHeader = (byte)((firstByte & 0xE0) | (FUHeader & Common.Binary.FiveBitMaxValue));
//Could have been SPS / PPS / SEI
if (nalHeader > 5)
{
if (nalHeader == 6)
{
Buffer.WriteByte(0);
containsSei = true;
}
else if (nalHeader == 7)
{
Buffer.WriteByte(0);
containsPps = true;
}
else if (nalHeader == 8)
{
Buffer.WriteByte(0);
containsSps = true;
}
}
if (nalHeader == 1) containsSlice = true;
if (nalHeader == 5) isIdr = true;
//Write the start code
Buffer.Write(NalStart, 0, 3);
//Write the re-construced header
Buffer.WriteByte(nalHeader);
}
//Write the data of the fragment.
Buffer.Write(packetData, offset, fragment_size);
}
}
return;
}
default:
{
// 6 SEI, 7 and 8 are SPS and PPS
if (nalUnitType > 5)
{
if (nalUnitType == 6)
{
Buffer.WriteByte(0);
containsSei = true;
}
else if (nalUnitType == 7)
{
Buffer.WriteByte(0);
containsPps = true;
}
else if (nalUnitType == 8)
{
Buffer.WriteByte(0);
containsSps = true;
}
}
if (nalUnitType == 1) containsSlice = true;
if (nalUnitType == 5) isIdr = true;
//Write the start code
Buffer.Write(NalStart, 0, 3);
//Write the nal heaer and data data
Buffer.Write(packetData, offset, count - offset);
return;
}