The `dec_ctx->time_base` was incorrectly default set by avcodec_open2(), while `enc_ctx->time_base` was derived from `dec_ctx->framerate`. This mismatch could cause incorrect video duration in the output.
This patch corrects the issue by adjusting the `enc_ctx->time_base` calculation to account for `ticks_per_frame`, ensuring that the time base is consistent between the decoder and encoder contexts.
--- Begin Message ---From 6a02fbaf6c6068040640ff105ad70115fb81b5d2 Mon Sep 17 00:00:00 2001 From: Jack Lau <jacklau122...@gmail.com> Date: Tue, 4 Feb 2025 21:39:20 +0800 Subject: [PATCH] examples/transcoding: Fix time_base handling X-Unsent: 1 To: ffmpeg-devel@ffmpeg.org The `dec_ctx->time_base` was incorrectly default set by avcodec_open2(), while `enc_ctx->time_base` was derived from `dec_ctx->framerate`. This mismatch could cause incorrect video duration in the output. This patch corrects the issue by adjusting the `enc_ctx->time_base` calculation to account for `ticks_per_frame`, ensuring that the time base is consistent between the decoder and encoder contexts. Signed-off-by: Jack Lau <jacklau1...@qq.com> --- doc/examples/transcoding.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/doc/examples/transcoding.c b/doc/examples/transcoding.c index 013f89fc7d..8cc1991267 100644 --- a/doc/examples/transcoding.c +++ b/doc/examples/transcoding.c @@ -172,7 +172,7 @@ static int open_output_file(const char *filename) else enc_ctx->pix_fmt = dec_ctx->pix_fmt; /* video time_base can be set to whatever is handy and supported by encoder */ - enc_ctx->time_base = av_inv_q(dec_ctx->framerate); + enc_ctx->time_base = av_inv_q(av_mul_q(dec_ctx->framerate, (AVRational){dec_ctx->ticks_per_frame, 1})); } else { enc_ctx->sample_rate = dec_ctx->sample_rate; ret = av_channel_layout_copy(&enc_ctx->ch_layout, &dec_ctx->ch_layout); @@ -180,7 +180,7 @@ static int open_output_file(const char *filename) return ret; /* take first format from list of supported formats */ enc_ctx->sample_fmt = encoder->sample_fmts[0]; - enc_ctx->time_base = (AVRational){1, enc_ctx->sample_rate}; + enc_ctx->time_base = (AVRational){1,dec_ctx->sample_rate}; } if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER) -- 2.48.1
--- End Message ---
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