[FFmpeg-devel] [PATCH 1/2] lavf: fall back to a more meaningful log instance name

[FFmpeg-devel] [PATCH 1/2] lavf: fall back to a more meaningful log instance name

[Anton Khirnov]

An uninitialized AVFormatContext instance with neither iformat nor
oformat set will currently log as 'NULL', which is confusing and
unhelpful. Print 'AVFormatContext' instead, which provides more
information.

This happens e.g. if choosing an output format fails in
avformat_alloc_output_context2().
---
 libavformat/options.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/options.c b/libavformat/options.c
index 22ad523b2d..e4a3aceed0 100644
--- a/libavformat/options.c
+++ b/libavformat/options.c
@@ -44,7 +44,7 @@ static const char* format_to_name(void* ptr)
     AVFormatContext* fc = (AVFormatContext*) ptr;
     if(fc->iformat) return fc->iformat->name;
     else if(fc->oformat) return fc->oformat->name;
-    else return "NULL";
+    else return fc->av_class->class_name;
 }
 
 static void *format_child_next(void *obj, void *prev)
-- 
2.39.1

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[FFmpeg-devel] [PATCH 2/2] lavf/mux: clarify log messages when choosing oformat fails

[Anton Khirnov]

Current log messages talk about 'suitable' output formats. This is
confusing, because it suggests that some formats are suitable, while
others are not, which is not the case.

Also, suggest possible user actions when format cannot be guessed from a
filename.
---
 libavformat/mux.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/libavformat/mux.c b/libavformat/mux.c
index 0bc9b6b87d..415bd3948f 100644
--- a/libavformat/mux.c
+++ b/libavformat/mux.c
@@ -102,7 +102,7 @@ int avformat_alloc_output_context2(AVFormatContext **avctx, const AVOutputFormat
         if (format) {
             oformat = av_guess_format(format, NULL, NULL);
             if (!oformat) {
-                av_log(s, AV_LOG_ERROR, "Requested output format '%s' is not a suitable output format\n", format);
+                av_log(s, AV_LOG_ERROR, "Requested output format '%s' is not known.\n", format);
                 ret = AVERROR(EINVAL);
                 goto error;
             }
@@ -110,8 +110,10 @@ int avformat_alloc_output_context2(AVFormatContext **avctx, const AVOutputFormat
             oformat = av_guess_format(NULL, filename, NULL);
             if (!oformat) {
                 ret = AVERROR(EINVAL);
-                av_log(s, AV_LOG_ERROR, "Unable to find a suitable output format for '%s'\n",
-                       filename);
+                av_log(s, AV_LOG_ERROR,
+                       "Unable to choose an output format for '%s'; "
+                       "use a standard extension for the filename or specify "
+                       "the format manually.\n", filename);
                 goto error;
             }
         }
-- 
2.39.1

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Re: [FFmpeg-devel] [PATCH 1/2] lavf: fall back to a more meaningful log instance name

[Stefano Sabatini]

On date Thursday 2023-03-30 11:38:07 +0200, Anton Khirnov wrote:
> An uninitialized AVFormatContext instance with neither iformat nor
> oformat set will currently log as 'NULL', which is confusing and
> unhelpful. Print 'AVFormatContext' instead, which provides more
> information.
> 
> This happens e.g. if choosing an output format fails in
> avformat_alloc_output_context2().
> ---
>  libavformat/options.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavformat/options.c b/libavformat/options.c
> index 22ad523b2d..e4a3aceed0 100644
> --- a/libavformat/options.c
> +++ b/libavformat/options.c
> @@ -44,7 +44,7 @@ static const char* format_to_name(void* ptr)
>      AVFormatContext* fc = (AVFormatContext*) ptr;
>      if(fc->iformat) return fc->iformat->name;
>      else if(fc->oformat) return fc->oformat->name;
> -    else return "NULL";
> +    else return fc->av_class->class_name;
>  }

Do you have an example to show? Anyway LGTM.
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Re: [FFmpeg-devel] [PATCH 2/2] lavf/mux: clarify log messages when choosing oformat fails

[Stefano Sabatini]

On date Thursday 2023-03-30 11:38:08 +0200, Anton Khirnov wrote:
> Current log messages talk about 'suitable' output formats. This is
> confusing, because it suggests that some formats are suitable, while
> others are not, which is not the case.
> 
> Also, suggest possible user actions when format cannot be guessed from a
> filename.
> ---
>  libavformat/mux.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/libavformat/mux.c b/libavformat/mux.c
> index 0bc9b6b87d..415bd3948f 100644
> --- a/libavformat/mux.c
> +++ b/libavformat/mux.c
> @@ -102,7 +102,7 @@ int avformat_alloc_output_context2(AVFormatContext **avctx, const AVOutputFormat
>          if (format) {
>              oformat = av_guess_format(format, NULL, NULL);
>              if (!oformat) {
> -                av_log(s, AV_LOG_ERROR, "Requested output format '%s' is not a suitable output format\n", format);
> +                av_log(s, AV_LOG_ERROR, "Requested output format '%s' is not known.\n", format);
>                  ret = AVERROR(EINVAL);
>                  goto error;
>              }
> @@ -110,8 +110,10 @@ int avformat_alloc_output_context2(AVFormatContext **avctx, const AVOutputFormat
>              oformat = av_guess_format(NULL, filename, NULL);
>              if (!oformat) {
>                  ret = AVERROR(EINVAL);
> -                av_log(s, AV_LOG_ERROR, "Unable to find a suitable output format for '%s'\n",
> -                       filename);
> +                av_log(s, AV_LOG_ERROR,
> +                       "Unable to choose an output format for '%s'; "
> +                       "use a standard extension for the filename or specify "
> +                       "the format manually.\n", filename);

LGTM.
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Re: [FFmpeg-devel] [PATCH 1/2] lavf: fall back to a more meaningful log instance name

[Anton Khirnov]

Quoting Stefano Sabatini (2023-04-02 21:06:35)
> On date Thursday 2023-03-30 11:38:07 +0200, Anton Khirnov wrote:
> > An uninitialized AVFormatContext instance with neither iformat nor
> > oformat set will currently log as 'NULL', which is confusing and
> > unhelpful. Print 'AVFormatContext' instead, which provides more
> > information.
> > 
> > This happens e.g. if choosing an output format fails in
> > avformat_alloc_output_context2().
> > ---
> >  libavformat/options.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/libavformat/options.c b/libavformat/options.c
> > index 22ad523b2d..e4a3aceed0 100644
> > --- a/libavformat/options.c
> > +++ b/libavformat/options.c
> > @@ -44,7 +44,7 @@ static const char* format_to_name(void* ptr)
> >      AVFormatContext* fc = (AVFormatContext*) ptr;
> >      if(fc->iformat) return fc->iformat->name;
> >      else if(fc->oformat) return fc->oformat->name;
> > -    else return "NULL";
> > +    else return fc->av_class->class_name;
> >  }
> 
> Do you have an example to show? Anyway LGTM.

./ffmpeg -i /tmp/s.mkv -f foobar -y /dev/null
before: [NULL @ 0x5580377834c0] Requested output format 'foobar' is not a suitable output format
after:  [AVFormatContext @ 0x55fa15bb34c0] Requested output format 'foobar' is not a suitable output format

-- 
Anton Khirnov
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