feat: add default X-TIMESTAMP-MAP header for empty subtitle files in WebVTT for HLS compatibility

Author: AbHash-RixE

docs/CHANGES.TXT

@@ -1,5 +1,6 @@
 1.0 (to be released)
 -----------------
+- IMPROVEMENT: Add default X-TIMESTAMP-MAP header for empty subtitle files in WebVTT for better compatibility of HLS streaming (#1743)
 - Fix: HardSubX OCR on Rust
 - Removed the Share Module
 - Fix: Regression failures on DVD files

src/ccextractor.c

@@ -6,6 +6,7 @@ License: GPL 2.0
 #include "ccextractor.h"
 #include <stdio.h>
 #include <locale.h>
+#include <ccx_encoders_helpers.h>
 
 volatile int terminate_asap = 0;
 
@@ -138,10 +139,27 @@ int start_ccx()
 #endif
 	terminate_asap = 0;
 
+#ifdef ENABLE_SHARING
+	if (ccx_options.translate_enabled && ctx->num_input_files > 1)
+	{
+		mprint("[share] WARNING: simultaneous translation of several input files is not supported yet\n");
+		ccx_options.translate_enabled = 0;
+		ccx_options.sharing_enabled = 0;
+	}
+	if (ccx_options.translate_enabled)
+	{
+		mprint("[share] launching translate service\n");
+		ccx_share_launch_translator(ccx_options.translate_langs, ccx_options.translate_key);
+	}
+#endif // ENABLE_SHARING
 	ret = 0;
 	while (switch_to_next_file(ctx, 0))
 	{
 		prepare_for_new_file(ctx);
+#ifdef ENABLE_SHARING
+		if (ccx_options.sharing_enabled)
+			ccx_share_start(ctx->basefilename);
+#endif // ENABLE_SHARING
 
 		stream_mode = ctx->demux_ctx->get_stream_mode(ctx->demux_ctx);
 		// Disable sync check for raw formats - they have the right timeline.
@@ -293,6 +311,14 @@ int start_ccx()
 			dec_ctx->timing->fts_now = 0;
 			dec_ctx->timing->fts_max = 0;
 
+#ifdef ENABLE_SHARING
+			if (ccx_options.sharing_enabled)
+			{
+				ccx_share_stream_done(ctx->basefilename);
+				ccx_share_stop();
+			}
+#endif // ENABLE_SHARING
+
 			if (dec_ctx->total_pulldownframes)
 				mprint("incl. pulldown frames:  %s  (%u frames at %.2ffps)\n",
 				       print_mstime_static((LLONG)(dec_ctx->total_pulldownframes * 1000 / current_fps)),
@@ -391,6 +417,7 @@ int start_ccx()
 	dinit_libraries(&ctx);
 
 	if (!ret)
+		webvtt_write_minimal_header();
 		mprint("\nNo captions were found in input.\n");
 
 	print_end_msg();

src/lib_ccx/ccx_common_option.h

@@ -198,6 +198,17 @@ struct ccx_s_options // Options from user parameters
 #ifdef WITH_LIBCURL
 	char *curlposturl;
 #endif
+
+
+#ifdef ENABLE_SHARING
+	//CC sharing
+	int sharing_enabled;
+	char *sharing_url;
+	//Translating
+	int translate_enabled;
+	char *translate_langs;
+	char *translate_key;
+#endif
 };
 
 extern struct ccx_s_options ccx_options;

src/lib_ccx/ccx_encoders_helpers.c

@@ -3,6 +3,9 @@
 #include "ccx_common_constants.h"
 #include "ccx_common_structs.h"
 #include "ccx_decoders_common.h"
+#include "ccx_encoders_common.h"
+#include "utility.h"
+#include "lib_ccx.h"
 
 #include <assert.h>
 
@@ -487,3 +490,33 @@ void ccx_encoders_helpers_perform_shellsort_words(void)
 	shell_sort(capitalization_list.words, capitalization_list.len, sizeof(*capitalization_list.words), string_cmp_function, NULL);
 	shell_sort(profane.words, profane.len, sizeof(*profane.words), string_cmp_function, NULL);
 }
+
+void webvtt_write_minimal_header()
+{	
+	struct lib_ccx_ctx *ctx = NULL;
+	// Initialize CCExtractor libraries
+	ctx = init_libraries(&ccx_options);
+
+    struct encoder_ctx *enc_ctx = NULL;
+
+    if (ccx_options.write_format == CCX_OF_WEBVTT && ccx_options.timestamp_map) {
+        // Initialize encoder with encoder_cfg
+        enc_ctx = init_encoder(&ccx_options.enc_cfg);
+
+        if (enc_ctx) {
+            const char *xtimestamp_line = ccx_options.enc_cfg.line_terminator_lf
+                ? "X-TIMESTAMP-MAP=MPEGTS:0,LOCAL:00:00:00.000\n\n"
+                : "X-TIMESTAMP-MAP=MPEGTS:0,LOCAL:00:00:00.000\r\n\r\n";
+
+            int used = encode_line(enc_ctx, enc_ctx->buffer, (unsigned char *)xtimestamp_line);
+
+            // fh is already an int fd
+            write_wrapped(enc_ctx->out->fh, (const char *)enc_ctx->buffer, used);
+
+            enc_ctx->wrote_webvtt_header = 1;
+
+            // Proper cleanup
+            dinit_encoder(&enc_ctx, 0);
+        }
+    }
+}

src/lib_ccx/ccx_encoders_helpers.h

@@ -49,4 +49,6 @@ void shell_sort(void *base, int nb, size_t size, int (*compar)(const void *p1, c
 
 void ccx_encoders_helpers_perform_shellsort_words(void);
 void ccx_encoders_helpers_setup(enum ccx_encoding_type encoding, int no_font_color, int no_type_setting, int trim_subs);
+
+void webvtt_write_minimal_header(void);
 #endif