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FEATURE: Add V_MPEG2 track support in MKV demuxer for CC extraction #2152

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Merged
cfsmp3 merged 3 commits into from
Feb 28, 2026
Merged

FEATURE: Add V_MPEG2 track support in MKV demuxer for CC extraction #2152

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934398f
feat: support V_MPEG2 tracks in MKV demuxer for CC extraction
Varadraj75 Feb 28, 2026
0cf5abf
style: apply clang-format to matroska.c
Varadraj75 Feb 28, 2026
a87ad2b
style: remove BOM from matroska.c
Varadraj75 Feb 28, 2026
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30 changes: 26 additions & 4 deletions src/lib_ccx/matroska.c
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
#include "lib_ccx.h"
#include "lib_ccx.h"
#include "utility.h"
#include "matroska.h"
#include "ccx_encoders_helpers.h"
Expand Down Expand Up @@ -691,7 +691,8 @@ void parse_simple_block(struct matroska_ctx *mkv_ctx, ULLONG frame_timestamp)
int is_avc = (track == mkv_ctx->avc_track_number);
int is_hevc = (track == mkv_ctx->hevc_track_number);

if (!is_avc && !is_hevc)
int is_mpeg2 = (track == mkv_ctx->mpeg2_track_number);
if (!is_avc && !is_hevc && !is_mpeg2)
{
// Skip everything except AVC/HEVC tracks
skip_bytes(file, len - 1); // 1 byte for track
Expand All @@ -710,6 +711,8 @@ void parse_simple_block(struct matroska_ctx *mkv_ctx, ULLONG frame_timestamp)

if (is_hevc)
process_hevc_frame_mkv(mkv_ctx, frame);
else if (is_mpeg2)
process_mpeg2_frame_mkv(mkv_ctx, frame);
else
process_avc_frame_mkv(mkv_ctx, frame);

Expand All @@ -723,6 +726,19 @@ static long bswap32(long v)
return swapped;
}

int process_mpeg2_frame_mkv(struct matroska_ctx *mkv_ctx, struct matroska_avc_frame frame)
{
struct lib_cc_decode *dec_ctx = update_decoder_list(mkv_ctx->ctx);
struct encoder_ctx *enc_ctx = update_encoder_list(mkv_ctx->ctx);
// Set timing from frame timestamp
set_current_pts(dec_ctx->timing, frame.FTS * (MPEG_CLOCK_FREQ / 1000));
set_fts(dec_ctx->timing);
// Use the existing MPEG-2 elementary stream processor (same as mp4.c and general_loop.c)
process_m2v(enc_ctx, dec_ctx, frame.data, frame.len, &mkv_ctx->dec_sub);
mkv_ctx->current_second = (int)(get_fts(dec_ctx->timing, dec_ctx->current_field) / 1000);
return 0;
}

int process_avc_frame_mkv(struct matroska_ctx *mkv_ctx, struct matroska_avc_frame frame)
{
int status = 0;
Expand Down Expand Up @@ -940,6 +956,8 @@ void parse_segment_track_entry(struct matroska_ctx *mkv_ctx)
mkv_ctx->avc_track_number = track_number;
else if (strcmp((const char *)codec_id_string, (const char *)hevc_codec_id) == 0)
mkv_ctx->hevc_track_number = track_number;
else if (strcmp((const char *)codec_id_string, (const char *)mpeg2_codec_id) == 0)
mkv_ctx->mpeg2_track_number = track_number;
MATROSKA_SWITCH_BREAK(code, code_len);
case MATROSKA_SEGMENT_TRACK_CODEC_PRIVATE:
// We handle DVB's private data differently
Expand Down Expand Up @@ -2042,6 +2060,7 @@ int matroska_loop(struct lib_ccx_ctx *ctx)
memset(&mkv_ctx->dec_sub, 0, sizeof(mkv_ctx->dec_sub));
mkv_ctx->avc_track_number = -1;
mkv_ctx->hevc_track_number = -1;
mkv_ctx->mpeg2_track_number = -1;

matroska_parse(mkv_ctx);

Expand All @@ -2055,6 +2074,7 @@ int matroska_loop(struct lib_ccx_ctx *ctx)
int sentence_count = mkv_ctx->sentence_count;
int avc_track_found = mkv_ctx->avc_track_number > -1;
int hevc_track_found = mkv_ctx->hevc_track_number > -1;
int mpeg2_track_found = mkv_ctx->mpeg2_track_number > -1;
int got_output = mkv_ctx->dec_sub.got_output;

matroska_free_all(mkv_ctx);
Expand All @@ -2068,10 +2088,12 @@ int matroska_loop(struct lib_ccx_ctx *ctx)
mprint("Found AVC track. ");
else if (hevc_track_found)
mprint("Found HEVC track. ");
else if (mpeg2_track_found)
mprint("Found MPEG2 track. ");
else
mprint("Found no AVC/HEVC track. ");
mprint("Found no AVC/HEVC/MPEG2 track. ");

if (got_output)
if (got_output || mpeg2_track_found)
return 1;
return sentence_count;
}
3 changes: 3 additions & 0 deletions src/lib_ccx/matroska.h
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Original file line number Diff line number Diff line change
Expand Up @@ -184,6 +184,7 @@ char *matroska_track_text_subtitle_id_extensions[] = {

char *avc_codec_id = "V_MPEG4/ISO/AVC";
char *hevc_codec_id = "V_MPEGH/ISO/HEVC";
char *mpeg2_codec_id = "V_MPEG2";
char *dvb_codec_id = "S_DVBSUB";

/* Messages */
Expand Down Expand Up @@ -247,6 +248,7 @@ struct matroska_ctx
struct cc_subtitle dec_sub;
int avc_track_number; // ID of AVC track. -1 if there is none
int hevc_track_number; // ID of HEVC track. -1 if there is none
int mpeg2_track_number; // ID of MPEG2 track. -1 if there is none
int sub_tracks_count;
int block_index;
int sentence_count;
Expand Down Expand Up @@ -278,6 +280,7 @@ void parse_segment_cluster(struct matroska_ctx *mkv_ctx);
void parse_simple_block(struct matroska_ctx *mkv_ctx, ULLONG frame_timestamp);
int process_avc_frame_mkv(struct matroska_ctx *mkv_ctx, struct matroska_avc_frame frame);
int process_hevc_frame_mkv(struct matroska_ctx *mkv_ctx, struct matroska_avc_frame frame);
int process_mpeg2_frame_mkv(struct matroska_ctx *mkv_ctx, struct matroska_avc_frame frame);
void parse_segment_track_entry(struct matroska_ctx *mkv_ctx);
void parse_private_codec_data(struct matroska_ctx *mkv_ctx, char *codec_id_string, ULLONG track_number, char *lang);
void parse_segment_tracks(struct matroska_ctx *mkv_ctx);
Expand Down
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