Libavcodec mpeg4 avi encoding framerate and timebase problem - frame-rate

Question

I try to generate a video with a timebase more precise than the 1/fps (camera frame rate are not constant). But the generated AVI does not seem to take into account the framerate that I indicate.
#include <iostream>
extern "C" {
#include "libavformat/avformat.h"
#include "libavcodec/avcodec.h"
}
#pragma comment(lib,"avcodec.lib")
#pragma comment(lib,"avformat.lib")
constexpr int TIMEFACTOR = 10;
static void encodeFrame(AVCodecContext *avctx, AVFormatContext *ctx, AVFrame* frame)
{
int ret = avcodec_send_frame(avctx, frame);
AVPacket packet;
av_init_packet(&packet);
ret = 0;
while (ret >= 0) {
ret = avcodec_receive_packet(avctx, &packet);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
return; // nothing to write
};
//packet.pts = (frame) ? frame->pts : packet.pts;
av_packet_rescale_ts(&packet, avctx->time_base, ctx->streams[0]->time_base);
packet.duration = TIMEFACTOR;
av_interleaved_write_frame(ctx, &packet);
av_packet_unref(&packet);
}
}
static void fill_yuv_frame(AVFrame* frame, int width, int height, int frameId)
{
// Y
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
frame->data[0][y * frame->linesize[0] + x] = x + y + frameId * 3;
}
}
// Cb and Cr
for (int y = 0; y < height / 2; y++) {
for (int x = 0; x < width / 2; x++) {
frame->data[1][y * frame->linesize[1] + x] = 128 + y + frameId * 2;
frame->data[2][y * frame->linesize[2] + x] = 64 + x + frameId * 5;
}
}
}
int main(int argc, char** argv)
{
const char filename[] = "output.avi";
const char encoder[] = "mpeg4";
constexpr int WIDTH = 640;
constexpr int HEIGHT = 480;
av_log_set_level(AV_LOG_DEBUG);
//delete file because libavcodec reload file
remove(filename);
AVFormatContext* ofmtCtx;
int ret = avformat_alloc_output_context2(&ofmtCtx, NULL, "avi", filename);
AVCodec* avcodec = avcodec_find_encoder_by_name(encoder);
AVCodecContext* avctx = avcodec_alloc_context3(avcodec);
avctx->width = WIDTH ;
avctx->height = HEIGHT ;
avctx->sample_aspect_ratio = { 1, 1 };
avctx->pix_fmt = AV_PIX_FMT_YUV420P; //Do not work with other type
avctx->codec_id = AV_CODEC_ID_MPEG4;
avctx->bit_rate = 4 * 1000 * 1000;
avctx->time_base = av_make_q(1, 25 * TIMEFACTOR);
avctx->framerate = av_make_q(25, 1);
avctx->ticks_per_frame = TIMEFACTOR;
avctx->gop_size = 10;
avctx->max_b_frames = 1;
AVStream* m_outStream = avformat_new_stream(ofmtCtx, NULL);
ret = avcodec_open2(avctx, avcodec, NULL);
ret = avcodec_parameters_from_context(m_outStream->codecpar, avctx);
m_outStream->time_base = avctx->time_base;
m_outStream->r_frame_rate = avctx->framerate;
m_outStream->avg_frame_rate = avctx->framerate;
ret = avio_open(&(ofmtCtx->pb),
filename,
AVIO_FLAG_WRITE);
ret = avformat_write_header(ofmtCtx, NULL);
av_dump_format(ofmtCtx, 0, filename, 1);
AVFrame * avframe = av_frame_alloc();
avframe->format = avctx->pix_fmt;
avframe->width = avctx->width;
avframe->height = avctx->height;
ret = av_frame_get_buffer(avframe, 0);
ret = av_frame_make_writable(avframe);
for (int i = 0; i < 25; ++i) {
fflush(stdout);
fill_yuv_frame(avframe, avctx->width, avctx->height, i);
avframe->pts = i * TIMEFACTOR;
encodeFrame(avctx, ofmtCtx, avframe);
}
encodeFrame(avctx, ofmtCtx, NULL);
av_write_trailer(ofmtCtx);
return 0;
}
And this is dump output :
[mpeg4 # 000002AA64FA1880] intra_quant_bias = 0 inter_quant_bias = -64
[file # 000002AA64F69AC0] Setting default whitelist 'file,crypto'
[avi # 000002AA64F73400] reserve_index_space:0 master_index_max_size:256
[avi # 000002AA64F73400] duration_est:36000.000, filesize_est:18.4GiB, master_index_max_size:256
Output #0, avi, to 'output.avi':
Metadata:
ISFT : Lavf58.12.100
Stream #0:0, 0, 1/250: Video: mpeg4, 1 reference frame (FMP4 / 0x34504D46), yuv420p, 640x480 (0x0) [SAR 1:1 DAR 4:3], 0/1, q=2-31, 4000 kb/s, 25 fps, 25 tbr, 250 tbn
But if I open the video in ffmpeg command line fps is 250, and video content 250 frames, with many dropframe.