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fix: correctly initialize frame type for tx3g and mov_text subtitles #2321

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fix: correctly initialize frame type for tx3g and mov_text subtitles #2321

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e3f3964
fix: correctly initialize frame type for tx3g and mov_text subtitles
shubhrai23 Aug 12, 2026
6e1e22a
fix: update comment and condition order for subtitle tracks
shubhrai23 Aug 14, 2026
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4 changes: 2 additions & 2 deletions src/lib_ccx/mp4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1121,11 +1121,11 @@ int processmp4(struct lib_ccx_ctx *ctx, struct ccx_s_mp4Cfg *cfg, char *file)
const LLONG timestamp = (LLONG)((sample->DTS + sample->CTS_Offset) * 1000) / timescale;
#endif
set_current_pts(dec_ctx->timing, (sample->DTS + sample->CTS_Offset) * MPEG_CLOCK_FREQ / timescale);
// For caption-only tracks (c608/c708), set frame type to I-frame
// For subtitle and caption-only tracks, set frame type to I-frame
// so that set_fts() will set min_pts from the first sample.
// Without video frames, frame type would stay Unknown and
// min_pts would never be set, causing broken timestamps.
if (type == GF_ISOM_MEDIA_CLOSED_CAPTION)
if (type == GF_ISOM_MEDIA_TEXT || type == GF_ISOM_MEDIA_SUBT || type == GF_ISOM_MEDIA_CLOSED_CAPTION)
dec_ctx->timing->current_picture_coding_type = CCX_FRAME_TYPE_I_FRAME;
set_fts(dec_ctx->timing);

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