[FFmpeg-user] I found the bugs

[Jim DeLaHunt]

On 2024-06-13 13:16, Mark Filipak wrote:
> On 13/06/2024 02.16, Carl Zwanzig wrote:
>> On 6/12/2024 2:44 PM, Mark Filipak wrote:
>>>
>>> I need someone more knowledgeable about FFmpeg to triage. 
>>
>> They're often called 'developers'.
>
> Okay, Carl. https://trac.ffmpeg.org/ticket/11055
>
> Since there are so many things wrong, I predict the devs will do nothing.

Mark, I agree with Carl that it is a better choice to turn your findings 
into a bug report than to wait for replies to an ffmpeg-user list post.  
Good for you for writing ticket #11055.

However, let me anticipate the feedback of developers reading this 
ticket: it is not yet a good bug report.  The FFmpeg project has advice 
on what to include in a bug report at 
<https://ffmpeg.org/bugreports.html>. The advice includes:

> // When writing your bug report, please include (uncompressed):
>
>   * What you were trying to accomplish (e.g., "I am trying to
>     transcode from this format to that format...")
>   * The problem you encountered (e.g., "ffmpeg crashed, see the gdb
>     and valgrind output below" or "The output video was all green")
>   * The exact command line you were using (e.g., "|ffmpeg -i input.mov
>     -an -vcodec foo output.avi|")
>   * The full, uncut console output provided by |ffmpeg -v 9 -loglevel
>     99 -i | followed by the name of your input file (copy/pasted from
>     the console, including the banner that indicates version and
>     configuration options), paste ffplay or ffprobe output only if
>     your problem is not reproducible with ffmpeg.
>   * Sufficient information, including any required input files, to
>     reproduce the bug and confirm a potential fix.
>
I don't see a clear statement of what you are trying to accomplish. I 
think it is: "I am trying to generate a video file which has correct PTS 
and DTS values and which plays correctly on MPV and FFplay, by splicing 
two video files together." But maybe it is: "I am trying to get FFmpeg's 
-vf showinfo filter and its -show_frames option to output consistent 
numbers."

I think you made a good faith effort to state the problem you 
encountered, but I think you did not follow through and explain your 
data. You don't explain what each of your columns depict (though maybe 
someone more expert than me would understand from just your column 
headers). You say, "'-vf showinfo' disagree: 53 frames, gap & 
duplicates.", but you don't say with what showinfo disagrees, and you 
don't point out which frames demonstrate the disagreement, which 
demonstrate gaps, which demonstrate duplicates. Maybe an additional 
column or so would be a good place to codes to denote disagreement, 
gaps, and/or duplicates.

You do supply the exact command lines you used. You also specified which 
version of FFmpeg you used. Good for you! But I don't see that you 
supplied "The full, uncut console output provided by ffmpeg -v 9 
-loglevel 99"….

I don't see where you supply the required input files to reproduce the 
99-frame output video or the diagnostics you list.

Part of the process of bug fixing is to convert information from the bug 
reporter's context and frame of reference to the bug fixer's context and 
frame of reference. Someone has to do that work.  One of the reasons why 
bugs don't get fixed is that the work doesn't get done.  If you really 
want the bug to get fixed, maybe you will have to do more of that work 
than you prefer to.

I hope this is helpful.  And, I hope your work turns into a solid 
improvement in FFmpeg. It has good potential to.
      —Jim DeLaHunt