[FFmpeg-devel] [PATCH v3 3/5] avfilter/vf_showinfo: display user data unregistered message

[Limin Wang]

On Fri, Dec 20, 2019 at 02:30:23PM -0300, James Almer wrote:
> On 12/19/2019 2:09 AM, lance.lmwang at gmail.com wrote:
> > From: Limin Wang <lance.lmwang at gmail.com>
> > 
> > Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> > ---
> >  libavfilter/vf_showinfo.c | 33 +++++++++++++++++++++++++++++++++
> >  1 file changed, 33 insertions(+)
> > 
> > diff --git a/libavfilter/vf_showinfo.c b/libavfilter/vf_showinfo.c
> > index 31f6b32aa4..bb3b37e0c5 100644
> > --- a/libavfilter/vf_showinfo.c
> > +++ b/libavfilter/vf_showinfo.c
> > @@ -169,6 +169,36 @@ static void dump_content_light_metadata(AVFilterContext *ctx, AVFrameSideData *s
> >             metadata->MaxCLL, metadata->MaxFALL);
> >  }
> >  
> > +static int string_is_ascii(const uint8_t *str)
> > +{
> > +    while (*str && *str < 128) str++;
> 
> I don't think the buffer is guaranteed to end with \0. You have
> sd->size, so you should probably use that, while also ensuring it ends
> with a \0 so the av_log below using %s works as intended.

If the str has any '\0', it'll end immediately, even < sd->size still, for the 
print %s will work like that. In case it's end without '\0', we don't
consider it's string, so it'll not print out like binary code.

Below is the example:
'hello\0'    will print hello
'hello\0tty' will print hello
'hello'      don't print

> 
> Also < 128 includes DEL. And you're not checking for >= 32.

I consider LF(\r), CR(\n) should be expected ascii, for example the
string may be json format, so I change to include all valid ascii
including the control character(0-31 and 121).
For example

'hello\ncc'    will print hello
                           cc

> 
> > +    return !*str;
> > +}
> > +
> > +static void dump_user_data_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, "%x", user_data[i]);
> > +    av_log(ctx, AV_LOG_INFO, "\n");
> > +
> > +    user_data += uuid_size;
> > +    /* Only print the user data details if it's string */
> > +    if (string_is_ascii(user_data)) {
> > +        av_log(ctx, AV_LOG_INFO, "User Data=");
> > +        av_log(ctx, AV_LOG_INFO, "%s", user_data);
> > +    }
> > +}
> > +
> >  static void dump_color_property(AVFilterContext *ctx, AVFrame *frame)
> >  {
> >      const char *color_range_str     = av_color_range_name(frame->color_range);
> > @@ -319,6 +349,9 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
> >              av_log(ctx, AV_LOG_INFO, "GOP timecode - %s", tcbuf);
> >              break;
> >          }
> > +        case AV_FRAME_DATA_USER_DATA_UNREGISTERED:
> > +            dump_user_data_unregistered_metadata(ctx, sd);
> > +            break;
> >          default:
> >              av_log(ctx, AV_LOG_WARNING, "unknown side data type %d (%d bytes)",
> >                     sd->type, sd->size);
> > 
> 
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