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Feature/ttml isobmff validation #2074

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d017f95
fix(webvtt): add default X-TIMESTAMP-MAP when timing info is missing
mohithshuka Jan 23, 2026
bcad7dc
Merge remote-tracking branch 'upstream/master'
mohithshuka Jan 29, 2026
8d54d3e
Add TTML subtitle format support
mohithshuka Jan 29, 2026
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30 changes: 27 additions & 3 deletions src/lib_ccx/ccx_encoders_webvtt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -230,13 +230,37 @@ void write_webvtt_header(struct encoder_ctx *context)
else
{
// Must have another newline if X-TIMESTAMP-MAP is not used
if (ccx_options.enc_cfg.line_terminator_lf == 1) // If -lf parameter is set.
// if (ccx_options.enc_cfg.line_terminator_lf == 1) // If -lf parameter is set.
// {
// write_wrapped(context->out->fh, "\n", 1);
// }
// else
// {
// write_wrapped(context->out->fh, "\r\n", 2);
// }
// Issue #1743: write default X-TIMESTAMP-MAP when timing info is unavailable
if (ccx_options.timestamp_map)
{
write_wrapped(context->out->fh, "\n", 1);
const char *default_header =
ccx_options.enc_cfg.line_terminator_lf
? "X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:0\n\n"
: "X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:0\r\n\r\n";

write_wrapped(context->out->fh,
default_header,
strlen(default_header));
}
else
{
write_wrapped(context->out->fh, "\r\n", 2);
// Must have another newline if X-TIMESTAMP-MAP is not used
if (ccx_options.enc_cfg.line_terminator_lf == 1)
{
write_wrapped(context->out->fh, "\n", 1);
}
else
{
write_wrapped(context->out->fh, "\r\n", 2);
}
}
}

Expand Down
124 changes: 124 additions & 0 deletions src/lib_ccx/ttml.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,124 @@
#include "ttml.h"
#include "ccx_encoders_common.h"
#include "utility.h"
#include "ccx_common_timing.h"
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

// Initialize TTML encoder context
void ttml_init(struct ttml_ctx *ctx, struct encoder_ctx *parent)
{
ctx->parent = parent;
ctx->wrote_header = 0;
ctx->last_start_time = 0;
ctx->last_end_time = 0;
}

// Write TTML XML header
int ttml_write_header(struct ttml_ctx *ctx)
{
if (ctx->wrote_header)
return 0;

const char *header =
"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
"<tt xmlns=\"http://www.w3.org/ns/ttml\"\n"
" xmlns:tts=\"http://www.w3.org/ns/ttml#styling\">\n"
" <head>\n"
" <styling>\n"
" <style xml:id=\"defaultStyle\" tts:fontFamily=\"monospace\" "
"tts:fontSize=\"1c\" tts:color=\"white\"/>\n"
" </styling>\n"
" </head>\n"
" <body>\n"
" <div>\n";

write(ctx->parent->out->fh, header, strlen(header));
ctx->wrote_header = 1;
return 0;
}

// Write TTML footer
int ttml_write_footer(struct ttml_ctx *ctx)
{
const char *footer =
" </div>\n"
" </body>\n"
"</tt>\n";

write(ctx->parent->out->fh, footer, strlen(footer));
return 0;
}

// Convert timestamp to TTML format (HH:MM:SS.mmm)
static void timestamp_to_ttml(int64_t timestamp, char *buffer, size_t bufsize)
{
int hours = (int)(timestamp / 3600000);
int minutes = (int)((timestamp % 3600000) / 60000);
int seconds = (int)((timestamp % 60000) / 1000);
int milliseconds = (int)(timestamp % 1000);

snprintf(buffer, bufsize, "%02d:%02d:%02d.%03d",
hours, minutes, seconds, milliseconds);
}

// Write a single subtitle entry in TTML format
int ttml_write_subtitle(struct ttml_ctx *ctx, struct cc_subtitle *sub)
{
if (!ctx->wrote_header)
ttml_write_header(ctx);

char start_time[32];
char end_time[32];

timestamp_to_ttml(sub->start_time, start_time, sizeof(start_time));
timestamp_to_ttml(sub->end_time, end_time, sizeof(end_time));

// Write opening tag
char buffer[256];
snprintf(buffer, sizeof(buffer),
" <p begin=\"%s\" end=\"%s\" style=\"defaultStyle\">\n",
start_time, end_time);
write(ctx->parent->out->fh, buffer, strlen(buffer));

// Write subtitle text (with proper XML escaping)
for (int i = 0; i < sub->nb_data; i++) {
unsigned char c = sub->data[i];

if (c == '<')
write(ctx->parent->out->fh, "&lt;", 4);
else if (c == '>')
write(ctx->parent->out->fh, "&gt;", 4);
else if (c == '&')
write(ctx->parent->out->fh, "&amp;", 5);
else if (c == '"')
write(ctx->parent->out->fh, "&quot;", 6);
else if (c == '\n')
write(ctx->parent->out->fh, "<br/>", 5);
else
write(ctx->parent->out->fh, &c, 1);
}

// Write closing tag
const char *close_tag = "\n </p>\n";
write(ctx->parent->out->fh, close_tag, strlen(close_tag));

return 0;
}

// Main write function called by encoder framework
int write_ttml(struct cc_subtitle *sub, struct encoder_ctx *context)
{
struct ttml_ctx *ctx = (struct ttml_ctx *)context->private_data;

if (!ctx) {
ctx = (struct ttml_ctx *)malloc(sizeof(struct ttml_ctx));
if (!ctx)
return -1;
ttml_init(ctx, context);
context->private_data = ctx;
}

return ttml_write_subtitle(ctx, sub);
}
30 changes: 30 additions & 0 deletions src/lib_ccx/ttml.h
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Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
#ifndef TTML_H
#define TTML_H

#include "ccx_common_platform.h"
#include "ccx_encoders_common.h"

// TTML encoder context
struct ttml_ctx {
struct encoder_ctx *parent;
int wrote_header;
int64_t last_start_time;
int64_t last_end_time;
};

// Initialize TTML encoder
void ttml_init(struct ttml_ctx *ctx, struct encoder_ctx *parent);

// Write TTML header
int ttml_write_header(struct ttml_ctx *ctx);

// Write TTML subtitle entry
int ttml_write_subtitle(struct ttml_ctx *ctx, struct cc_subtitle *sub);

// Write TTML footer
int ttml_write_footer(struct ttml_ctx *ctx);

// Encode a single screen to TTML
int write_ttml(struct cc_subtitle *sub, struct encoder_ctx *context);

#endif // TTML_H
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