[FFmpeg-devel] [PATCH] lavf/img2enc: mention -vframes in error output

[Moritz Barsnick]

On Mon, Jul 11, 2016 at 13:31:08 -0800, Lou Logan wrote:
> On Mon, 11 Jul 2016 21:08:40 +0000 (UTC), Carl Eugen Hoyos wrote:
> > Lou Logan <lou <at> lrcd.com> writes:
> > > or use -vframes 1 to output single image)\n",  
> > 
> > Since this is a muxer and -vframes is an ffmpeg option, 
> > I am not convinced this is a good solution.
> > Note that -vsync vfr also "fixes" ticket #5701.
> 
> I know this is not a muxer specific option, but I thought it would
> still be useful to general users, because, according to what I have

I (sort of) read Carl Eugen's answer as a remark that this is a
library, which is not necessarily driven by ffmpeg. So the message may
need to be generic, such as:

 "Could not get frame filename number %d from pattern '%s' (either "
 "set -updatefirst, or use a pattern like %%03d within the filename "
 "pattern, or ensure that the application requests only one single "
 "frame (e.g. \"-frames:v 1\" option to ffmpeg)\n",

(Note that "-updatefirst" is also an ffmpeg command line option if you
prepend the dash. You could write: "... use the \"updatefirst\" muxer
option, [...]")

Moritz

P.S.: Some muxers have a similar situation, referring to ffmpeg command
      line options from the library:
            av_log(s, AV_LOG_ERROR, "H.264 bitstream malformed, "
                   "no startcode found, use the video bitstream filter 'h264_mp4toannexb' to fix it "
                   "('-bsf:v h264_mp4toannexb' option with ffmpeg)\n");