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fix(mp4): Fix 200ms timing offset for MOV/MP4 caption extraction #1915

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Merged
cfsmp3 merged 1 commit into from
Dec 28, 2025
Merged

fix(mp4): Fix 200ms timing offset for MOV/MP4 caption extraction #1915

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19 changes: 19 additions & 0 deletions src/lib_ccx/mp4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -202,6 +202,13 @@ static int process_xdvb_track(struct lib_ccx_ctx *ctx, const char *basename, GF_

dec_ctx = update_decoder_list(ctx);
enc_ctx = update_encoder_list(ctx);

// Set buffer data type to CCX_PES for MP4/MOV MPEG-2 tracks.
// This ensures cb_field counters are not incremented in do_cb(),
// which is correct because container formats associate captions
// with the frame's PTS directly.
dec_ctx->in_bufferdatatype = CCX_PES;

if ((sample_count = gf_isom_get_sample_count(f, track)) < 1)
{
return 0;
Expand Down Expand Up @@ -249,6 +256,12 @@ static int process_avc_track(struct lib_ccx_ctx *ctx, const char *basename, GF_I

dec_ctx = update_decoder_list(ctx);

// Set buffer data type to CCX_H264 for MP4/MOV AVC tracks.
// This ensures cb_field counters are not incremented in do_cb(),
// which is correct because container formats associate captions
// with the frame's PTS directly.
dec_ctx->in_bufferdatatype = CCX_H264;

if ((sample_count = gf_isom_get_sample_count(f, track)) < 1)
{
return 0;
Expand Down Expand Up @@ -326,6 +339,12 @@ static int process_hevc_track(struct lib_ccx_ctx *ctx, const char *basename, GF_
// Enable HEVC mode
dec_ctx->avc_ctx->is_hevc = 1;

// Set buffer data type to CCX_H264 for MP4/MOV HEVC tracks.
// This ensures cb_field counters are not incremented in do_cb(),
// which is correct because container formats associate captions
// with the frame's PTS directly.
dec_ctx->in_bufferdatatype = CCX_H264;

if ((sample_count = gf_isom_get_sample_count(f, track)) < 1)
{
return 0;
Expand Down
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