[RFC PATCH v2 13/13] apps: cam: Write raw file if PPM cannot be written

[Milan Zamazal]

Hi Laurent,

thank you for review.

Laurent Pinchart <laurent.pinchart at ideasonboard.com> writes:

> Hi Milan,
>
> Thank you for the patch.
>
> On Fri, Jan 24, 2025 at 10:58:04PM +0100, Milan Zamazal wrote:
>> `cam' application can be requested to write its output as a PPM file.
>> However, this is supported only for certain formats (only BGR888
>> currently).  If the output format cannot be written, `cam' reports an
>> error and doesn't write anything.
>> 
>> This is all right with a single stream input but impractical with
>> multiple streams of different output formats (e.g. a processed stream +
>> a raw stream) where some of them can be written in the supported format
>> while the other not.  In such a case, it's better to write the supported
>> formats as PPM files and the unsupported formats as raw files, with the
>> corresponding warning on stderr.  `.raw' extension is added to the file
>> name in such a case to make clear it's not a PPM file.
>> 
>> This is a sort of hack but serves the purpose for the moment.
>
> Should we instead change the -F option (and the -D and -S options too I
> suppose) to act at the stream level instead of the camera level ?

Something like this would be useful.  But maybe rather than changing the
given options (how?), it would be simpler to add a keyword to -s,
e.g. output=file/sdl/kms.  What do you think?

>> Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
>> ---
>>  src/apps/cam/file_sink.cpp | 16 +++++++++++-----
>>  1 file changed, 11 insertions(+), 5 deletions(-)
>> 
>> diff --git a/src/apps/cam/file_sink.cpp b/src/apps/cam/file_sink.cpp
>> index 76e21db9..1a866137 100644
>> --- a/src/apps/cam/file_sink.cpp
>> +++ b/src/apps/cam/file_sink.cpp
>> @@ -7,6 +7,7 @@
>>  
>>  #include <array>
>>  #include <assert.h>
>> +#include <errno.h>
>>  #include <fcntl.h>
>>  #include <iomanip>
>>  #include <iostream>
>> @@ -133,11 +134,16 @@ void FileSink::writeBuffer(const Stream *stream, FrameBuffer *buffer,
>>  	if (fileType_ == FileType::Ppm) {
>>  		ret = PPMWriter::write(filename.c_str(), stream->configuration(),
>>  				       image->data(0));
>> -		if (ret < 0)
>> -			std::cerr << "failed to write PPM file `" << filename
>> -				  << "'" << std::endl;
>> -
>> -		return;
>> +		if (ret == -EINVAL) {
>> +			filename += ".raw";
>> +			std::cerr << "cannot write file in PPM format, writing `"
>> +				  << filename << "' instead" << std::endl;
>> +		} else {
>> +			if (ret < 0)
>> +				std::cerr << "failed to write PPM file `" << filename
>> +					  << "'" << std::endl;
>> +			return;
>> +		}
>>  	}
>>  
>>  	fd = open(filename.c_str(), O_CREAT | O_WRONLY |