[FFmpeg-devel] [PATCH 1/5] Move timestamp correction code from ffplay to cmdutils

[Michael Niedermayer]

On Mon, Jul 26, 2010 at 01:16:06PM -0700, Alexander Strange wrote:
> ---
>  cmdutils.c |   27 +++++++++++++++++++++++++++
>  cmdutils.h |   24 ++++++++++++++++++++++++
>  ffplay.c   |   31 ++++++-------------------------
>  3 files changed, 57 insertions(+), 25 deletions(-)
> 
> diff --git a/cmdutils.c b/cmdutils.c
> index 978b73c..cd0b194 100644
> --- a/cmdutils.c
> +++ b/cmdutils.c


>  
> -            is->last_dts_for_fault_detection=
> -            is->last_pts_for_fault_detection= INT64_MIN;
> +            init_pts_correction(&is->pts_ctx);

> @@ -663,3 +663,30 @@ int read_file(const char *filename, char **bufptr, size_t *size)
>      fclose(f);
>      return 0;
>  }
> +
> +void init_pts_correction(PtsCorrectionContext *ctx)
> +{
> +    ctx->num_faulty_pts = ctx->num_faulty_dts = 0;
> +    ctx->last_pts = ctx->last_dts = AV_NOPTS_VALUE;

INT64_MIN is correct, AV_NOPTS_VALUE is wrong, the code depends on it being
the smallest integer, it does not check == AV_NOPTS_VALUE


> +}
> +
> +int64_t guess_correct_pts(PtsCorrectionContext *ctx, int64_t reordered_pts, int64_t dts)
> +{
> +    int64_t pts = AV_NOPTS_VALUE;
> +
> +    if (dts != AV_NOPTS_VALUE) {
> +        ctx->num_faulty_dts += dts <= ctx->last_dts;
> +        ctx->last_dts = dts;
> +    }
> +    if (reordered_pts != AV_NOPTS_VALUE) {
> +        ctx->num_faulty_pts += reordered_pts <= ctx->last_pts;
> +        ctx->last_pts = reordered_pts;
> +    }
> +    if ((ctx->num_faulty_pts<ctx->num_faulty_dts || dts == AV_NOPTS_VALUE)
> +       && reordered_pts != AV_NOPTS_VALUE)
> +        pts = reordered_pts;
> +    else
> +        pts = dts;
> +
> +    return pts;
> +}

you are loosing the decoder_reorder_pts code here


> diff --git a/cmdutils.h b/cmdutils.h
> index d48abab..f2ad34a 100644
> --- a/cmdutils.h
> +++ b/cmdutils.h
> @@ -220,4 +220,28 @@ int read_yesno(void);
>   */
>  int read_file(const char *filename, char **bufptr, size_t *size);
>  
> +typedef struct {
> +    int64_t num_faulty_pts; /// Number of incorrect PTS values so far
> +    int64_t num_faulty_dts; /// Number of incorrect DTS values so far
> +    int64_t last_pts;       /// PTS of the last frame
> +    int64_t last_dts;       /// DTS of the last frame
> +} PtsCorrectionContext;
> +
> +/**
> + * Resets the state of the PtsCorrectionContext.
> + */
> +void init_pts_correction(PtsCorrectionContext *ctx);
> +
> +/**
> + * Attempts to guess proper monotonic timestamps for decoded video frames
> + * which might have incorrect times.
> + *
> + * @param pts The pts field of the decoded AVPacket, as passed through
> + * AVCodecContext.reordered_opaque
> + * @param dts The dts field of the decoded AVPacket

> + * @return Whichever of pts or dts is more correct; will not be less than
> + * or equal to the previous value. May be AV_NOPTS_VALUE.

this is impossible, mpeg-ps/ts have timestamp discontinuities and thus the
values may very well be less than previous

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Concerning the gods, I have no means of knowing whether they exist or not
or of what sort they may be, because of the obscurity of the subject, and
the brevity of human life -- Protagoras
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