Add SCC support for CEA-708 Decoder (CCExtractor#1426)

docs/CHANGES.TXT

@@ -1,5 +1,6 @@
 0.95 (to be released)
 -----------------
+- New: Add SCC Support for CEA-708 Decoder (#1426) 
 - Fix: crash in Rust decoder on ATSC1.0 TS Files (#1407)
 - Removed the --with-gui flag for linux/configure and mac/configure (use the Flutter GUI instead)
 - Fix: segmentation fault in using hardsubx

src/lib_ccx/ccx_decoders_708_output.c

@@ -335,6 +335,16 @@ unsigned char adjust_odd_parity(const unsigned char value)
     return value;
 }
 
+void dtvcc_write_scc_header(dtvcc_tv_screen *tv, struct encoder_ctx *encoder)
+{
+    char *buf = (char *)encoder->buffer;
+    // 18 characters long + 2 new lines
+    memset(buf, 0, 20);
+    sprintf(buf, "Scenarist_SCC V1.0\n\n");
+
+    write_wrapped(encoder->dtvcc_writers[tv->service_number - 1].fd, buf, strlen(buf));
+}
+
 void dtvcc_write_scc(dtvcc_writer_ctx *writer, dtvcc_service_decoder *decoder, struct encoder_ctx *encoder) {
     dtvcc_tv_screen *tv = decoder->tv;
 
@@ -345,11 +355,16 @@ void dtvcc_write_scc(dtvcc_writer_ctx *writer, dtvcc_service_decoder *decoder, s
         return;
 
     char *buf = (char *) encoder -> buffer;
+    if (tv->cc_count == 2) {
+        dtvcc_write_scc_header(tv, encoder);
+    }
     print_scc_time(tv->time_ms_show + encoder->subs_delay, buf);
+
+    // {clear buffer} {pop on caption} {row15 column1}
+    sprintf(buf+strlen(buf),"94ae 9420 9470 ");
+
     for (int i = 0; i < CCX_DTVCC_SCREENGRID_ROWS; i++) {
         if(!dtvcc_is_row_empty(tv,i)) {
-            // {clear buffer} {pop on caption} {row15 column1}
-            sprintf(buf+strlen(buf),"94ae 9420 9470 ");
             int first, last, bytes_written = 0;
             dtvcc_get_write_interval(tv, i, &first, &last);
             for (int j = first; j <= last; j++) {
@@ -359,16 +374,17 @@ void dtvcc_write_scc(dtvcc_writer_ctx *writer, dtvcc_service_decoder *decoder, s
                 }
                 bytes_written += 1;
             }
-            //filler 0x80 if the number of bytes written are not even
+            // if byte pair are not even then make it even by adding 0x80 as padding
             if (bytes_written % 2 == 1) {
-                sprintf(buf +strlen(buf), "80");
+                sprintf(buf +strlen(buf), "80 ");
+            }else {
+                sprintf(buf +strlen(buf), " ");
             }
-
         }
     }
     sprintf(buf +strlen(buf), "\n\n");
     write_wrapped(encoder->dtvcc_writers[tv->service_number - 1].fd,buf,strlen(buf));
-    // when hiding substract a frame
+    // when hiding subtract a frame
     // 1 frame = 34 ms
     print_scc_time(tv->time_ms_hide + encoder->subs_delay - 34, buf);
     // clear caption command
@@ -439,7 +455,6 @@ void dtvcc_write(dtvcc_writer_ctx *writer, dtvcc_service_decoder *decoder, struc
 			dtvcc_write_sami(writer, decoder, encoder);
 			break;
         case CCX_OF_SCC:
-            dtvcc_write_debug(decoder->tv);
             dtvcc_write_scc(writer, decoder, encoder);
             break;
 		case CCX_OF_MCC:

src/rust/src/decoder/timing.rs

@@ -47,3 +47,12 @@ pub fn get_time_str(time: LLONG) -> String {
     let ms = time - 1000 * (ss + 60 * (mm + 60 * hh));
     format!("{:02}:{:02}:{:02},{:03}", hh, mm, ss, ms)
 }
+
+///Returns a hh:mm:ss:frame string of time for SCC format
+pub fn get_scc_time_str(time: LLONG) -> String {
+    let hh = time / 1000 / 60 / 60;
+    let mm = time / 1000 / 60 - 60 * hh;
+    let ss = time / 1000 - 60 * (mm + 60 * hh);
+    let frame = ((time - 1000 * (ss + 60 * (mm + 60 * hh))) as f32 * 29.97/1000.00) as u8;
+    format!("{:02}:{:02}:{:02}:{:02}", hh, mm, ss, frame)
+}

src/rust/src/decoder/tv_screen.rs

@@ -10,7 +10,7 @@ use std::os::windows::io::IntoRawHandle;
 use std::{ffi::CStr, fs::File};
 
 use super::output::{color_to_hex, write_char, Writer};
-use super::timing::get_time_str;
+use super::timing::{get_time_str,get_scc_time_str};
 use super::{CCX_DTVCC_SCREENGRID_COLUMNS, CCX_DTVCC_SCREENGRID_ROWS};
 use crate::{
     bindings::*,
@@ -308,8 +308,8 @@ impl dtvcc_tv_screen {
     }
 
 
+    /// Write captions in SCC format
     pub fn write_scc(&self, writer: &mut Writer) -> Result<(), String> {
-
         fn adjust_odd_parity(value: u8) -> u8{
             let mut ones = 0;
             for j in 0..7 {
@@ -327,19 +327,20 @@ impl dtvcc_tv_screen {
             return Ok(());
         }
 
-        for row_index in 0..CCX_DTVCC_SCREENGRID_ROWS as usize {
-            if !self.is_row_empty(row_index) {
-                let time_show = get_time_str(self.time_ms_show);
-                let time_hide = get_time_str(self.time_ms_hide);
+        let mut buf = String::new();
+        let time_show = get_scc_time_str(self.time_ms_show);
+        let time_end = get_scc_time_str(self.time_ms_hide);
 
-                debug!("{} {}", time_show, time_hide);
+        buf.push_str(&time_show);
+        // {clear buffer} {start pop on} {row15 col0 white}
+        buf.push_str(" 94ae 9420 9470");
 
+        for row_index in 0..CCX_DTVCC_SCREENGRID_ROWS as usize {
+            if !self.is_row_empty(row_index) {
+                debug!("{}", time_show);
                 let (first, last) = self.get_write_interval(row_index);
                 debug!("First: {}, Last: {}", first, last);
 
-                let mut buf = String::new();
-                // {rollup} {unknown} {row15 col0 white}
-                buf.push_str("9426 94ad 9470");
                 let mut bytes_written = 0;
                 for i in 0..last + 1 {
                     if bytes_written % 2 == 0 {
@@ -348,18 +349,18 @@ impl dtvcc_tv_screen {
                     let adjusted_val = adjust_odd_parity(self.chars[row_index][i].sym as u8);
                     buf = format!("{}{:x}", buf, adjusted_val);
                     bytes_written += 1;
-                    // debug!(" value {:x} {} ",adjusted_val, (adjusted_val) as char);
                 }
-                // add 0x80 as filler if number of bytes is not even
+                // add 0x80 padding and form byte pair if the last byte pair is not form
                 if bytes_written % 2 == 1 {
                     buf.push_str("80");
                 }
-                buf.push_str("\r\n");
-
-                debug!("{}", buf);
-                writer.write_to_file(buf.as_bytes())?;
             }
         }
+        buf.push_str("\n\n");
+        writer.write_to_file(buf.as_bytes())?;
+        // clear screen
+        buf = format!("{} 942c 942c \n\n",time_end);
+        writer.write_to_file(buf.as_bytes())?;
         return Ok(());
     }