[FFmpeg-devel] [PATCH v11 3/4] avfilter/vf_showinfo: display H.26[45] user data unregistered sei message

[Andreas Rheinhardt]

lance.lmwang at gmail.com:
> From: Limin Wang <lance.lmwang at gmail.com>
> 
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---
>  libavfilter/vf_showinfo.c | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/libavfilter/vf_showinfo.c b/libavfilter/vf_showinfo.c
> index 5d4aee4..2511da5 100644
> --- a/libavfilter/vf_showinfo.c
> +++ b/libavfilter/vf_showinfo.c
> @@ -37,6 +37,7 @@
>  #include "libavutil/timecode.h"
>  #include "libavutil/mastering_display_metadata.h"
>  #include "libavutil/video_enc_params.h"
> +#include "libavutil/avstring.h"
>  
>  #include "avfilter.h"
>  #include "internal.h"
> @@ -190,6 +191,39 @@ static void dump_video_enc_params(AVFilterContext *ctx, AVFrameSideData *sd)
>          av_log(ctx, AV_LOG_INFO, "%u blocks; ", par->nb_blocks);
>  }
>  
> +static int string_is_print(const uint8_t *str)
> +{
> +    while (av_isgraph(*str)) str++;
> +    return !*str;

This is dangerous: The SEI message needn't be zero-terminated, so this
may segfault. Furthermore, it is also wrong: If the user data payload
happens to contain a binary zero preceded by printable ASCII characters,
it will be considered a string, even if there are unprintable characters
after the binary zero (which may really happen if the payload is
actually binary).

> +}
> +
> +static void dump_sei_unregistered_metadata(AVFilterContext *ctx, AVFrameSideData *sd)
> +{
> +    const int uuid_size = 16;
> +    uint8_t *user_data = sd->data;
> +
> +    if (sd->size < uuid_size) {
> +        av_log(ctx, AV_LOG_ERROR, "invalid data(%d < UUID(%d-bytes))", sd->size, uuid_size);
> +        return;
> +    }
> +
> +    av_log(ctx, AV_LOG_INFO, "User Data Unregistered:\n");
> +    av_log(ctx, AV_LOG_INFO, "UUID=");
> +    for (int i = 0; i < uuid_size; i++) {
> +        av_log(ctx, AV_LOG_INFO, "%02x", user_data[i]);
> +        if (i == 3 || i == 5 || i == 7 || i == 9)
> +            av_log(ctx, AV_LOG_INFO, "-");
> +    }
> +    av_log(ctx, AV_LOG_INFO, "\n");
> +
> +    user_data += uuid_size;
> +    /* Only print the user data details if it's string */
> +    if (string_is_print(user_data)) {
> +        av_log(ctx, AV_LOG_INFO, "User Data=");
> +        av_log(ctx, AV_LOG_INFO, "%s", user_data);

Given that the user_data needn't be zero-terminated, you must specify
the precision (i.e. the number of bytes to write) here.

> +    }
> +}
> +
>  static void dump_color_property(AVFilterContext *ctx, AVFrame *frame)
>  {
>      const char *color_range_str     = av_color_range_name(frame->color_range);
> @@ -375,6 +409,9 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
>          case AV_FRAME_DATA_VIDEO_ENC_PARAMS:
>              dump_video_enc_params(ctx, sd);
>              break;
> +        case AV_FRAME_DATA_SEI_UNREGISTERED:
> +            dump_sei_unregistered_metadata(ctx, sd);
> +            break;
>          default:
>              av_log(ctx, AV_LOG_WARNING, "unknown side data type %d (%d bytes)",
>                     sd->type, sd->size);
>