我正在尝试使用 libavcodec（版本 3.4.6）对 H.264 中的视频进行编码。当我使用软件编码器“libx264”时它可以工作，但是当我尝试将我的英特尔 cpu 的硬件编码器与 VAAPI 一起使用时它不起作用。通过 VAAPI 使用 ffmpeg 进行硬件编码可从命令行工作（使用此处的命令）。
显然，没有示例或教程如何使用 VAAPI 和 libav* 进行编码。我通读了涵盖相关用例（硬件解码、软件编码、复用）的ffmpeg 示例，并尝试相应地调整它们。
当我设置 VAAPI 编码器时，avcodec_open2()返回AVERROR(EINVAL)(-22) 并将以下错误消息打印到控制台：
AVCodecContext.pix_fmt 和 AVHWFramesContext.format 不匹配
Encoder::setupEncoder()您可以在我的代码末尾找到它。我错过了什么？
下面是我的代码，分为三个文件：
编码器.h
#ifndef ENCODER_H
#define ENCODER_H
#include <cassert>
extern "C" {
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavutil/opt.h>
#include <libavutil/hwcontext.h>
}
class Encoder
{
public:
Encoder(const bool hwAccel);
void addFrame(AVFrame* frame);
void flush();
static constexpr int s_width = 640;
static constexpr int s_height = 480;
static constexpr int s_fps = 25;
private:
void setup();
void setupEncoder();
void encodeFrame(AVFrame* frame);
// members
int m_frameId = 1;
const bool m_hardwareAcceleration = false;
AVCodecContext* m_encoder = nullptr;
AVFormatContext* m_muxer = nullptr;
AVStream* m_avStream = nullptr;
AVBufferRef* m_device = nullptr;
AVFrame* m_hwFrame = nullptr;
};
#endif // ENCODER_H
编码器.cpp
#include "encoder.h"
extern "C" {
static enum AVPixelFormat get_vaapi_format(AVCodecContext*, const enum AVPixelFormat *pix_fmts)
{
const enum AVPixelFormat *p;
for (p = pix_fmts; *p != AV_PIX_FMT_NONE; p++) {
if (*p == AV_PIX_FMT_VAAPI)
return *p;
}
fprintf(stderr, "Failed to get HW surface format.\n");
return AV_PIX_FMT_NONE;
}
}
Encoder::Encoder(const bool hwAccel)
: m_hardwareAcceleration(hwAccel)
{
setup();
}
void Encoder::addFrame(AVFrame* frame)
{
AVFrame* frameToEncode = frame;
if(m_hardwareAcceleration) {
assert(frame->format == AV_PIX_FMT_NV12);
av_hwframe_transfer_data(m_hwFrame, frame, 0);
assert(m_hwFrame->format == AV_PIX_FMT_VAAPI);
frameToEncode = m_hwFrame;
}
frameToEncode->pts = m_frameId++;
encodeFrame(frameToEncode);
}
void Encoder::flush()
{
encodeFrame(nullptr);
av_write_trailer(m_muxer);
}
void Encoder::setup()
{
assert(avformat_alloc_output_context2(&m_muxer, nullptr, "matroska", nullptr) == 0);
assert(m_muxer != nullptr);
setupEncoder();
m_avStream = avformat_new_stream(m_muxer, nullptr);
assert(m_avStream != nullptr);
m_avStream->id = m_muxer->nb_streams-1;
m_avStream->time_base = m_encoder->time_base;
// Some formats want stream headers to be separate.
if(m_muxer->oformat->flags & AVFMT_GLOBALHEADER)
m_encoder->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
assert(avcodec_parameters_from_context(m_avStream->codecpar, m_encoder) == 0);
assert(avio_open(&m_muxer->pb, m_hardwareAcceleration? "hardware.mkv": "software.mkv", AVIO_FLAG_WRITE) == 0);
assert(avformat_write_header(m_muxer, nullptr) == 0);
}
void Encoder::setupEncoder()
{
const char* encoderName = m_hardwareAcceleration? "h264_vaapi": "libx264";
AVCodec* videoCodec = avcodec_find_encoder_by_name(encoderName);
m_encoder = avcodec_alloc_context3(videoCodec);
m_encoder->bit_rate = s_width * s_height * s_fps * 2;
m_encoder->width = s_width;
m_encoder->height = s_height;
m_encoder->time_base = (AVRational){1, s_fps};
m_encoder->framerate = (AVRational){s_fps, 1};
m_encoder->gop_size = s_fps; // have at least 1 I-frame per second
m_encoder->max_b_frames = 1;
m_encoder->pix_fmt = AV_PIX_FMT_YUV420P;
if(m_hardwareAcceleration) {
m_encoder->pix_fmt = AV_PIX_FMT_VAAPI;
m_encoder->get_format = get_vaapi_format;
assert(av_hwdevice_ctx_create(&m_device, AV_HWDEVICE_TYPE_VAAPI, "/dev/dri/renderD128", nullptr, 0) == 0);
AVHWDeviceContext* deviceCtx = (AVHWDeviceContext*) m_device->data;
assert(deviceCtx->type == AV_HWDEVICE_TYPE_VAAPI);
m_encoder->hw_device_ctx = av_hwframe_ctx_alloc(m_device);
m_encoder->hw_frames_ctx = av_buffer_ref(m_device);
m_hwFrame = av_frame_alloc();
av_hwframe_get_buffer(m_encoder->hw_device_ctx, m_hwFrame, 0);
}
assert(avcodec_open2(m_encoder, videoCodec, nullptr) == 0); // <-- returns -22 (EINVAL) for hardware encoder
m_muxer->video_codec_id = videoCodec->id;
m_muxer->video_codec = videoCodec;
}
void Encoder::encodeFrame(AVFrame* frame)
{
assert(avcodec_send_frame(m_encoder, frame) == 0);
AVPacket packet;
av_init_packet(&packet);
int ret = 0;
while(ret >= 0) {
ret = avcodec_receive_packet(m_encoder, &packet);
if(ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
return; // nothing to write
}
assert(ret >= 0);
av_packet_rescale_ts(&packet, m_encoder->time_base, m_avStream->time_base);
packet.stream_index = m_avStream->index;
av_interleaved_write_frame(m_muxer, &packet);
av_packet_unref(&packet);
}
}
主文件
#include "encoder.h"
AVFrame* createFrame(const int format)
{
AVFrame* frame = av_frame_alloc();
frame->format = format;
frame->width = Encoder::s_width;
frame->height = Encoder::s_height;
assert(av_frame_get_buffer(frame, 0) == 0);
assert(av_frame_make_writable(frame) == 0);
// Y
for(int y=0; y<frame->height; y++) {
for(int x=0; x<frame->width; x++) {
frame->data[0][y * frame->linesize[0] + x] = 0;
}
}
// CbCr
const int widthCbCr = frame->width / 2;
const int heightCbCr = frame->height / 2;
if(format == AV_PIX_FMT_YUV420P) {
for(int y=0; y<heightCbCr; y++) {
for(int x=0; x<widthCbCr; x++) {
frame->data[1][y * frame->linesize[1] + x] = 0; // Cb
frame->data[2][y * frame->linesize[2] + x] = 0; // Cr
}
}
return frame;
}
else if(format == AV_PIX_FMT_NV12) {
for(int y=0; y<heightCbCr; y++) {
for(int x=0; x<widthCbCr; x++) {
frame->data[1][y * frame->linesize[0] + x] = 0;
}
}
return frame;
}
return nullptr;
}
int main()
{
av_register_all();
AVFrame* yuv420pFrame = createFrame(AV_PIX_FMT_YUV420P);
AVFrame* nv12Frame = createFrame(AV_PIX_FMT_NV12);
// works well
Encoder softwareEncoder(false);
for(int i=0; i<100; ++i)
softwareEncoder.addFrame(yuv420pFrame);
softwareEncoder.flush();
// does not work
Encoder hardwareEncoder(true);
for(int i=0; i<100; ++i)
hardwareEncoder.addFrame(nv12Frame);
hardwareEncoder.flush();
return 0;
}
请注意，我有意省略了各种 free() 函数和析构函数以保持代码简短。