Return timestamp info and tokens in offline ASR

Co-authored-by: zhangbaofeng@npnets.com <41259@Zbf>

@@ -8,7 +8,7 @@
 
 #include <algorithm>
 #include <cmath>
-
+#include "nlohmann/json.hpp"
 #include "kaldi-native-fbank/csrc/online-feature.h"
 #include "sherpa-onnx/csrc/macros.h"
 #include "sherpa-onnx/csrc/offline-recognizer.h"
@@ -214,5 +214,12 @@ void OfflineStream::SetResult(const OfflineRecognitionResult &r) {
 const OfflineRecognitionResult &OfflineStream::GetResult() const {
   return impl_->GetResult();
 }
+std::string OfflineRecognitionResult::AsJsonString() const {
+  nlohmann::json j;
+  j["text"] = text;
+  j["tokens"] = tokens;
+  j["timestamps"] = timestamps;
 
+  return j.dump();
+}
 }  // namespace sherpa_onnx

@@ -27,6 +27,8 @@ struct OfflineRecognitionResult {
   /// timestamps.size() == tokens.size()
   /// timestamps[i] records the time in seconds when tokens[i] is decoded.
   std::vector<float> timestamps;
+
+  std::string AsJsonString() const;
 };
 
 struct OfflineFeatureExtractorConfig {

@@ -100,10 +100,11 @@ void OfflineWebsocketDecoder::Decode() {
   for (int32_t i = 0; i != size; ++i) {
     connection_hdl hdl = handles[i];
     asio::post(server_->GetConnectionContext(),
-               [this, hdl, text = ss[i]->GetResult().text]() {
+               [this, hdl, result = ss[i]->GetResult()]() {
                  websocketpp::lib::error_code ec;
                  server_->GetServer().send(
-                     hdl, text, websocketpp::frame::opcode::text, ec);
+                     hdl, result.AsJsonString(),
+                     websocketpp::frame::opcode::text, ec);
                  if (ec) {
                    server_->GetServer().get_alog().write(
                        websocketpp::log::alevel::app, ec.message());

@@ -101,7 +101,7 @@ for a list of pre-trained models to download.
   fprintf(stderr, "Done!\n\n");
   for (int32_t i = 1; i <= po.NumArgs(); ++i) {
     fprintf(stderr, "%s\n%s\n----\n", po.GetArg(i).c_str(),
-            ss[i - 1]->GetResult().text.c_str());
+            ss[i - 1]->GetResult().AsJsonString().c_str());
   }
 
   float elapsed_seconds =