Agfdhyk

I want to encode frames from camera using NvPipe and stream them via RTP using FFmpeg. My code produces the following error when I want to decode the stream:

[h264 @ 0x7f3c6c007e80] decode_slice_header error

[h264 @ 0x7f3c6c007e80] non-existing PPS 0 referenced

[h264 @ 0x7f3c6c007e80] decode_slice_header error

[h264 @ 0x7f3c6c007e80] non-existing PPS 0 referenced

[h264 @ 0x7f3c6c007e80] decode_slice_header error

[h264 @ 0x7f3c6c007e80] non-existing PPS 0 referenced

[h264 @ 0x7f3c6c007e80] decode_slice_header error

[h264 @ 0x7f3c6c007e80] no frame!

[h264 @ 0x7f3c6c007e80] non-existing PPS 0 referenced    0B f=0/0   

    Last message repeated 1 times

On another PC, it is even not able to stream, and fails with an segmentation fault on av_interleaved_write_frame(..). How to initialize the AVPacket and its timebase correctly to successfully send and receive the stream using ffplay/VLC/ other software?

My code:

avformat_network_init();

// init encoder

AVPacket *pkt = new AVPacket();

int targetBitrate = 1000000;

int targetFPS = 30;

const uint32_t width = 640;

const uint32_t height = 480;



NvPipe* encoder = NvPipe_CreateEncoder(NVPIPE_BGRA32, NVPIPE_H264, NVPIPE_LOSSY, targetBitrate, targetFPS);



// init stream output

std::string str = "rtp://127.0.0.1:49990";

AVStream* stream = nullptr;

AVOutputFormat *output_format = av_guess_format("rtp", nullptr, nullptr);;

AVFormatContext *output_format_ctx = avformat_alloc_context();



avformat_alloc_output_context2(&output_format_ctx, output_format,   output_format->name, str.c_str());



// open output url

if (!(output_format->flags & AVFMT_NOFILE)){

     ret = avio_open(&output_format_ctx->pb, str.c_str(), AVIO_FLAG_WRITE);

}



output_format_ctx->oformat = output_format;

output_format->video_codec = AV_CODEC_ID_H264;



stream  = avformat_new_stream(output_format_ctx,nullptr);

stream->id = 0;

stream->codecpar->codec_id = AV_CODEC_ID_H264;

stream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;

stream->codecpar->width = width;

stream->codecpar->height = height;

stream->time_base.den = 1;

stream->time_base.num = targetFPS; // 30fps



/* Write the header */

avformat_write_header(output_format_ctx, nullptr); // this seems to destroy the timebase of the stream



std::vector<uint8_t> rgba(width * height * 4);

std::vector<uint8_t> compressed(rgba.size());

int frameCnt = 0;



// encoding and streaming

while (true) 

{

frameCnt++;

// Encoding

// Construct dummy frame

for (uint32_t y = 0; y < height; ++y)

    for (uint32_t x = 0; x < width; ++x)

        rgba[4 * (y * width + x) + 1] = (255.0f * x* y) / (width * height) * (y % 100 < 50);



uint64_t size = NvPipe_Encode(encoder, rgba.data(), width * 4, compressed.data(), compressed.size(), width, height, false); // last parameter needs to be true for keyframes



av_init_packet(pkt);

pkt->data = compressed.data();

pkt->size = size;

pkt->pts = frameCnt;



if(!memcmp(compressed.data(), "x00x00x00x01x67", 5)) {

    pkt->flags |= AV_PKT_FLAG_KEY;

}



//stream



fflush(stdout);



// Write the compressed frame into the output

pkt->pts = av_rescale_q(frameCnt, AVRational {1, targetFPS}, stream->time_base);

pkt->dts = pkt->pts;

pkt->stream_index = stream->index;



/* Write the data on the packet to the output format  */

av_interleaved_write_frame(output_format_ctx, pkt);



/* Reset the packet */

av_packet_unref(pkt); 

}

The .sdp file to open the stream with ffplay looks like this:

v=0

o=- 0 0 IN IP4 127.0.0.1

s=No Name

c=IN IP4 127.0.0.1

t=0 0

a=tool:libavformat 58.18.101

m=video 49990 RTP/AVP 96

a=rtpmap:96 H264/90000

a=fmtp:96 packetization-mode=1

The code above sends no keyframes (or I-frames). The (obvious) solution is to send keyframes by turning the last parameter of NvPipe_Encode() to true. To achieve a certain GOP size gop_size, do something like

NvPipe_Encode(encoder, rgba.data(), width * 4, compressed.data(), 

              compressed.size(), width, height, framecnt % gop_size == 0 ? true : false);