feat(mcap): add paced replay tooling

src/testers/mcap_reader_tester.cpp

@@ -7,6 +7,7 @@
 
 #include <cstdint>
 #include <expected>
+#include <fstream>
 #include <iostream>
 #include <optional>
 #include <string>
@@ -25,6 +26,7 @@ enum class TesterExitCode : int {
 	FormatMismatch = 7,
 	EmptyPayload = 8,
 	ThresholdError = 9,
+	DumpError = 10,
 };
 
 [[nodiscard]]
@@ -36,6 +38,7 @@ struct Config {
 	std::string input_path{};
 	std::optional<std::string> expected_topic{};
 	std::optional<std::string> expected_format{};
+	std::optional<std::string> dump_annexb_output{};
 	std::uint32_t min_messages{1};
 };
 
@@ -46,6 +49,7 @@ std::expected<Config, int> parse_args(int argc, char **argv) {
 	app.add_option("input", config.input_path, "Input MCAP path")->required();
 	app.add_option("--expect-topic", config.expected_topic, "Expected MCAP topic");
 	app.add_option("--expect-format", config.expected_format, "Expected CompressedVideo format");
+	app.add_option("--dump-annexb-output", config.dump_annexb_output, "Write concatenated CompressedVideo.data payloads to a file");
 	app.add_option("--min-messages", config.min_messages, "Minimum expected message count")->check(CLI::PositiveNumber);
 
 	try {
@@ -74,6 +78,15 @@ int main(int argc, char **argv) {
 	std::uint64_t message_count{0};
 	std::uint64_t previous_log_time{0};
 	bool saw_log_time{false};
+	std::optional<std::ofstream> dump_stream{};
+	if (config->dump_annexb_output) {
+		dump_stream.emplace(*config->dump_annexb_output, std::ios::binary | std::ios::trunc);
+		if (!dump_stream->is_open()) {
+			spdlog::error("failed to open dump output '{}'", *config->dump_annexb_output);
+			reader.close();
+			return exit_code(TesterExitCode::DumpError);
+		}
+	}
 
 	auto message_view = reader.readMessages();
 	for (auto it = message_view.begin(); it != message_view.end(); ++it) {
@@ -117,6 +130,14 @@ int main(int argc, char **argv) {
 			reader.close();
 			return exit_code(TesterExitCode::EmptyPayload);
 		}
+		if (dump_stream) {
+			dump_stream->write(message.data().data(), static_cast<std::streamsize>(message.data().size()));
+			if (!dump_stream->good()) {
+				spdlog::error("failed to write Annex B dump to '{}'", *config->dump_annexb_output);
+				reader.close();
+				return exit_code(TesterExitCode::DumpError);
+			}
+		}
 
 		previous_log_time = it->message.logTime;
 		saw_log_time      = true;