feat: add sprop-parameter-sets support to H264/H265 SDP

Add SetSPS/SetPPS methods to H264Source and SetVPS/SetSPS/SetPPS
to H265Source. When these parameters are set, GetAttribute() includes
them as base64-encoded sprop-parameter-sets in the SDP, allowing
clients to properly initialize decoders with correct video dimensions.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Isaac Connor

src/xop/H264Source.cpp

@@ -35,6 +35,28 @@ H264Source::~H264Source()
 
 }
 
+std::string H264Source::Base64Encode(const uint8_t* data, size_t size)
+{
+    static const char base64_chars[] =
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+    std::string result;
+    result.reserve(((size + 2) / 3) * 4);
+
+    for (size_t i = 0; i < size; i += 3) {
+        uint32_t n = (data[i] << 16);
+        if (i + 1 < size) n |= (data[i + 1] << 8);
+        if (i + 2 < size) n |= data[i + 2];
+
+        result += base64_chars[(n >> 18) & 0x3F];
+        result += base64_chars[(n >> 12) & 0x3F];
+        result += (i + 1 < size) ? base64_chars[(n >> 6) & 0x3F] : '=';
+        result += (i + 2 < size) ? base64_chars[n & 0x3F] : '=';
+    }
+
+    return result;
+}
+
 string H264Source::GetMediaDescription(uint16_t port)
 {
     char buf[100] = {0};
@@ -44,7 +66,31 @@ string H264Source::GetMediaDescription(uint16_t port)
 
 string H264Source::GetAttribute()
 {
-    return string("a=rtpmap:96 H264/90000");
+    string attr = "a=rtpmap:96 H264/90000";
+
+    // Add fmtp line with profile-level-id and sprop-parameter-sets if SPS/PPS available
+    if (!sps_.empty() && !pps_.empty()) {
+        // profile-level-id is bytes 1,2,3 of SPS (after NAL header)
+        uint32_t profile_level_id = 0;
+        if (sps_.size() >= 4) {
+            profile_level_id = (sps_[1] << 16) | (sps_[2] << 8) | sps_[3];
+        }
+
+        std::string sps_b64 = Base64Encode(sps_.data(), sps_.size());
+        std::string pps_b64 = Base64Encode(pps_.data(), pps_.size());
+
+        char buf[512];
+        sprintf(buf, "\r\na=fmtp:96 packetization-mode=1;profile-level-id=%06X;sprop-parameter-sets=%s,%s",
+                profile_level_id, sps_b64.c_str(), pps_b64.c_str());
+        attr += buf;
+    }
+
+    if (width_ > 0 && height_ > 0) {
+        char buf[64];
+        sprintf(buf, "\r\na=x-dimensions:%u,%u", width_, height_);
+        attr += buf;
+    }
+    return attr;
 }
 
 bool H264Source::HandleFrame(MediaChannelId channel_id, AVFrame frame)

src/xop/H264Source.h

@@ -6,6 +6,7 @@
 
 #include "MediaSource.h"
 #include "rtp.h"
+#include <vector>
 
 namespace xop
 { 
@@ -19,21 +20,39 @@ class H264Source : public MediaSource
 	void SetFramerate(uint32_t framerate)
 	{ framerate_ = framerate; }
 
-	uint32_t GetFramerate() const 
+	uint32_t GetFramerate() const
 	{ return framerate_; }
 
-	virtual std::string GetMediaDescription(uint16_t port); 
+	void SetResolution(uint32_t width, uint32_t height)
+	{ width_ = width; height_ = height; }
 
-	virtual std::string GetAttribute(); 
+	uint32_t GetWidth() const { return width_; }
+	uint32_t GetHeight() const { return height_; }
+
+	// Set SPS/PPS for sprop-parameter-sets in SDP
+	void SetSPS(const uint8_t* data, size_t size)
+	{ sps_.assign(data, data + size); }
+
+	void SetPPS(const uint8_t* data, size_t size)
+	{ pps_.assign(data, data + size); }
+
+	virtual std::string GetMediaDescription(uint16_t port);
+
+	virtual std::string GetAttribute();
 
 	virtual bool HandleFrame(MediaChannelId channel_id, AVFrame frame);
 
 	static int64_t GetTimestamp();
-	
+
 private:
 	H264Source(uint32_t framerate);
+	static std::string Base64Encode(const uint8_t* data, size_t size);
 
 	uint32_t framerate_ = 25;
+	uint32_t width_ = 0;
+	uint32_t height_ = 0;
+	std::vector<uint8_t> sps_;
+	std::vector<uint8_t> pps_;
 };
 
 }

src/xop/H265Source.cpp

@@ -32,7 +32,29 @@ H265Source* H265Source::CreateNew(uint32_t framerate)
 
 H265Source::~H265Source()
 {
-	
+
+}
+
+std::string H265Source::Base64Encode(const uint8_t* data, size_t size)
+{
+	static const char base64_chars[] =
+		"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+	std::string result;
+	result.reserve(((size + 2) / 3) * 4);
+
+	for (size_t i = 0; i < size; i += 3) {
+		uint32_t n = (data[i] << 16);
+		if (i + 1 < size) n |= (data[i + 1] << 8);
+		if (i + 2 < size) n |= data[i + 2];
+
+		result += base64_chars[(n >> 18) & 0x3F];
+		result += base64_chars[(n >> 12) & 0x3F];
+		result += (i + 1 < size) ? base64_chars[(n >> 6) & 0x3F] : '=';
+		result += (i + 2 < size) ? base64_chars[n & 0x3F] : '=';
+	}
+
+	return result;
 }
 
 string H265Source::GetMediaDescription(uint16_t port)
@@ -44,7 +66,26 @@ string H265Source::GetMediaDescription(uint16_t port)
 
 string H265Source::GetAttribute()
 {
-	return string("a=rtpmap:96 H265/90000");
+	string attr = "a=rtpmap:96 H265/90000";
+
+	// Add fmtp line with sprop-vps, sprop-sps, sprop-pps if available
+	if (!vps_.empty() && !sps_.empty() && !pps_.empty()) {
+		std::string vps_b64 = Base64Encode(vps_.data(), vps_.size());
+		std::string sps_b64 = Base64Encode(sps_.data(), sps_.size());
+		std::string pps_b64 = Base64Encode(pps_.data(), pps_.size());
+
+		char buf[1024];
+		sprintf(buf, "\r\na=fmtp:96 sprop-vps=%s;sprop-sps=%s;sprop-pps=%s",
+				vps_b64.c_str(), sps_b64.c_str(), pps_b64.c_str());
+		attr += buf;
+	}
+
+	if (width_ > 0 && height_ > 0) {
+		char buf[64];
+		sprintf(buf, "\r\na=x-dimensions:%u,%u", width_, height_);
+		attr += buf;
+	}
+	return attr;
 }
 
 bool H265Source::HandleFrame(MediaChannelId channelId, AVFrame frame)

src/xop/H265Source.h

@@ -6,6 +6,7 @@
 
 #include "MediaSource.h"
 #include "rtp.h"
+#include <vector>
 
 namespace xop
 {
@@ -19,21 +20,43 @@ class H265Source : public MediaSource
 	void Setframerate(uint32_t framerate)
 	{ framerate_ = framerate; }
 
-	uint32_t GetFramerate() const 
+	uint32_t GetFramerate() const
 	{ return framerate_; }
 
-	virtual std::string GetMediaDescription(uint16_t port=0); 
+	void SetResolution(uint32_t width, uint32_t height)
+	{ width_ = width; height_ = height; }
 
-	virtual std::string GetAttribute(); 
+	uint32_t GetWidth() const { return width_; }
+	uint32_t GetHeight() const { return height_; }
+
+	// Set VPS/SPS/PPS for sprop parameters in SDP
+	void SetVPS(const uint8_t* data, size_t size)
+	{ vps_.assign(data, data + size); }
+
+	void SetSPS(const uint8_t* data, size_t size)
+	{ sps_.assign(data, data + size); }
+
+	void SetPPS(const uint8_t* data, size_t size)
+	{ pps_.assign(data, data + size); }
+
+	virtual std::string GetMediaDescription(uint16_t port=0);
+
+	virtual std::string GetAttribute();
 
 	virtual bool HandleFrame(MediaChannelId channelId, AVFrame frame);
 
 	static int64_t GetTimestamp();
-	 
+
 private:
 	H265Source(uint32_t framerate);
+	static std::string Base64Encode(const uint8_t* data, size_t size);
 
 	uint32_t framerate_ = 25;
+	uint32_t width_ = 0;
+	uint32_t height_ = 0;
+	std::vector<uint8_t> vps_;
+	std::vector<uint8_t> sps_;
+	std::vector<uint8_t> pps_;
 };
 
 }