[libcamera-devel] [PATCH v2 3/4] cam: Extend request completion handler to deal with multiple streams

[Kieran Bingham]

Hi Niklas,

On 03/04/2019 02:12, Niklas Söderlund wrote:
> The completion handler needs to handle all buffers in the request. Solve
> this by iterating over all buffers in the completed request and assign
> each stream a name as we encounter them. The buffer writer needs to be
> extended to learn about stream names so it can prefix the files it
> writes with it.
> 
> Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> ---
>  src/cam/buffer_writer.cpp |  5 +++--
>  src/cam/buffer_writer.h   |  2 +-
>  src/cam/main.cpp          | 42 ++++++++++++++++++++++++++++-----------
>  3 files changed, 34 insertions(+), 15 deletions(-)
> 
> diff --git a/src/cam/buffer_writer.cpp b/src/cam/buffer_writer.cpp
> index 2d2258b4cd1cbbc2..b82ffaded688226a 100644
> --- a/src/cam/buffer_writer.cpp
> +++ b/src/cam/buffer_writer.cpp
> @@ -19,13 +19,14 @@ BufferWriter::BufferWriter(const std::string &pattern)
>  {
>  }
>  
> -int BufferWriter::write(libcamera::Buffer *buffer)
> +int BufferWriter::write(libcamera::Buffer *buffer,
> +			const std::string &streamName)
>  {
>  	std::string filename;
>  	size_t pos;
>  	int fd, ret = 0;
>  
> -	filename = pattern_;
> +	filename = streamName + "-" + pattern_;
>  	pos = filename.find_first_of('#');
>  	if (pos != std::string::npos) {
>  		std::stringstream ss;
> diff --git a/src/cam/buffer_writer.h b/src/cam/buffer_writer.h
> index 9705773e0e397d45..7bf785d1e83235ff 100644
> --- a/src/cam/buffer_writer.h
> +++ b/src/cam/buffer_writer.h
> @@ -16,7 +16,7 @@ class BufferWriter
>  public:
>  	BufferWriter(const std::string &pattern = "frame-#.bin");
>  
> -	int write(libcamera::Buffer *buffer);
> +	int write(libcamera::Buffer *buffer, const std::string &streamName);
>  
>  private:
>  	std::string pattern_;
> diff --git a/src/cam/main.cpp b/src/cam/main.cpp
> index b47bda21cbb7f220..9af7907a3d937c28 100644
> --- a/src/cam/main.cpp
> +++ b/src/cam/main.cpp
> @@ -145,28 +145,46 @@ static int prepareCameraConfig(std::map<Stream *, StreamConfiguration> *config)
>  	return 0;
>  }
>  
> +static std::string streamToName(const Stream *stream)
> +{
> +	static std::map<const Stream *, std::string> names;
> +
> +	if (names.find(stream) == names.end())
> +		names[stream] = std::string("stream") + std::to_string(names.size());
> +
> +	return names[stream];
> +}
> +
>  static void requestComplete(Request *request, const std::map<Stream *, Buffer *> &buffers)
>  {
>  	static uint64_t last = 0;
> +	double fps = 0.0;
>  
>  	if (request->status() == Request::RequestCancelled)
>  		return;
>  
> -	Buffer *buffer = buffers.begin()->second;
> +	for (auto it = buffers.begin(); it != buffers.end(); ++it) {
> +		Stream *stream = it->first;
> +		Buffer *buffer = it->second;
> +		std::string name = streamToName(stream);
>  
> -	double fps = buffer->timestamp() - last;
> -	fps = last && fps ? 1000000000.0 / fps : 0.0;
> -	last = buffer->timestamp();
> +		if (it == buffers.begin()) {
> +			fps = buffer->timestamp() - last;
> +			fps = last && fps ? 1000000000.0 / fps : 0.0;
> +			last = buffer->timestamp();
> +		}


Should we track FPS on a per stream basis? Here you are really
calculating Requests (with at least one buffer) per second, which might
be a perfectly reasonable thing to calculate, but what if (as a simple
extreme) I queued up requests to alternate between two streams A and B.

--------
R:1 A
R:2    B
R:3 A
R:4    B
--------

Is that 4 frames per interval? or two?


It might be worth splitting the calculation out to a function and
storing the result on a per stream basis without using static locals.

>  
> -	std::cout << "seq: " << std::setw(6) << std::setfill('0') << buffer->sequence()
> -		  << " buf: " << buffer->index()
> -		  << " bytesused: " << buffer->bytesused()
> -		  << " timestamp: " << buffer->timestamp()
> -		  << " fps: " << std::fixed << std::setprecision(2) << fps
> -		  << std::endl;
> +		std::cout << name << " seq: " << std::setw(6)
> +			  << std::setfill('0') << buffer->sequence()
> +			  << " buf: " << buffer->index()
> +			  << " bytesused: " << buffer->bytesused()
> +			  << " timestamp: " << buffer->timestamp()
> +			  << " fps: " << std::fixed << std::setprecision(2) << fps
> +			  << std::endl;
>  
> -	if (writer)
> -		writer->write(buffer);
> +		if (writer)
> +			writer->write(buffer, name);
> +	}
>  
>  	request = camera->createRequest();
>  	if (!request) {
> 

-- 
Regards
--
Kieran