mozaic/lib/av/av.cpp

#include "av.hpp"

extern "C" {
#include <libavutil/frame.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
}

#include <string>
#include <cassert>

namespace av {

	format_context format_open_input(const std::string& filename, AVInputFormat* format, AVDictionary** options){
		AVFormatContext * ctx = nullptr;
		avformat_open_input(&ctx, filename.c_str(), format, options);
		if(!ctx) throw error("Unable to open input " + filename);
		// This might be optional, but AFAIK people always do this after opening input
		avformat_find_stream_info(ctx, options);
		return {ctx, [](auto x){ avformat_close_input(&x); }};
	}

	format_context format_alloc_context(){
		auto ptr = avformat_alloc_context();
		if(!ptr) throw error("Could not allocate AVFormatContext");
		return {avformat_alloc_context(), &avformat_free_context};
	}


	codec find_encoder(AVCodecID codec_id){
		auto ptr = avcodec_find_encoder(codec_id);
		if(!ptr) throw error("Could not find codec");
		return {ptr, nullptr};
	}

	codec_context context_alloc(codec const & codec){
		auto ptr = avcodec_alloc_context3(codec.get());
		if(!ptr) throw av::error("Could not allocate codec context");
		return {ptr, [](auto x){ avcodec_free_context(&x); }};
	}

	codec_context context_from_stream(format_context const & ctx, size_t i){
		return {ctx->streams[i]->codec, nullptr};
	}


	open_guard codec_open(codec_context & ctx, codec const & codec, AVDictionary** options){
		if(!ctx) throw error("Invalid codec context");
		if(!codec) throw error("Invalid codec");
		if(avcodec_open2(ctx.get(), codec.get(), options) < 0) throw error("Could not open codec");
		return {ctx.get(), [](auto x){ avcodec_close(x); }};
	}


	packet read_frame(format_context& ctx, packet_buffer& p){
		auto ret = av_read_frame(ctx.get(), &p);
		if(ret < 0){
			return {nullptr, &av_free_packet};
		} else {
			return {&p, &av_free_packet};
		}
	}


	frame frame_alloc() {
		auto ptr = av_frame_alloc();
		if(!ptr) throw error("Could not allocate AVFrame");
		return {ptr, [](auto x){ av_frame_free(&x); }};
	}

	frame frame_clone(const frame& f){
		auto ptr = av_frame_clone(f.get());
		if(!ptr) throw error("Could not clone AVFrame");
		return {ptr, [](auto x){ av_frame_free(&x); }};
	}

	AVPixelFormat get_format(const frame& f){
		return static_cast<AVPixelFormat>(f->format);
	}

	void crop(frame& f, int left, int top, int width, int height){
		f = crop(std::move(f), left, top, width, height);
	}

	frame crop(frame&& f, int left, int top, int width, int height){
		// if(left + width > f->width || top + height > f->height) throw error("Crop sizes do not match");

		auto ptr = reinterpret_cast<AVPicture*>(f.get());
		auto ret = av_picture_crop(ptr, ptr, av::get_format(f), top, left);
		if(ret < 0) throw error("Could not crop");

		f->width = width;
		f->height = height;
		return std::move(f);
	}

	frame crop(const frame& f, int left, int top, int width, int height){
		return crop(frame_clone(f), left, top, width, height);
	}

}