libx264 Input picture width (640) is greater than stride (0) - ffmpeg

Question

I'm trying to encode a series of Cairo surfaces by using libav. Here I initialize AV stuff:
AVStream* video_stream;
AVCodec* vcodec;
gint ret;
/* Setup video container */
avformat_alloc_output_context2(&img->video_format_context, NULL, NULL, filename);
if (img->video_format_context == NULL)
{
img_message(img, TRUE, _("Failed to find a suitable container for %s\n"),filename);
return FALSE;
}
ret = avio_open(&img->video_format_context->pb, filename, AVIO_FLAG_WRITE);
if (ret < 0)
{
img_message(img, TRUE, _("Couldn't write output file %s\n"),filename);
return FALSE;
}
/* Setup video codec */
vcodec = avcodec_find_encoder(codec_id);
if (!vcodec)
{
img_message(img, TRUE, _("Couldn't find any encoder for %s\n"),filename);
return FALSE;
}
/* Create video stream */
video_stream = avformat_new_stream(img->video_format_context, vcodec);
video_stream->id = 0;
if (! video_stream)
{
img_message(img, TRUE, _("Couldn't not allocate video stream\n"));
return FALSE;
}
/* Allocate video encoding context */
img->codec_context = avcodec_alloc_context3(vcodec);
if (! img->codec_context)
{
img_message(img, TRUE, _("Couldn't allocate video enconding context\n"));
return FALSE;
}
/* Setup video enconding context parameters */
img->codec_context->codec_id = codec_id;
img->codec_context->codec_type = AVMEDIA_TYPE_VIDEO;
img->codec_context->width = img->video_size[0];
img->codec_context->height = img->video_size[1];
img->codec_context->sample_aspect_ratio = (struct AVRational) {1, 1};
img->codec_context->pix_fmt = vcodec->pix_fmts[0];
img->codec_context->framerate = av_d2q(frame_rate, INT_MAX);
if (codec_id == AV_CODEC_ID_VP8 || codec_id == AV_CODEC_ID_VP9 || codec_id == AV_CODEC_ID_THEORA || codec_id == AV_CODEC_ID_FLV1 ||
AV_CODEC_ID_MPEG1VIDEO || codec_id == AV_CODEC_ID_MPEG2VIDEO)
img->codec_context->bit_rate = round(bitrate_crf * 1000000);
img->codec_context->time_base = av_inv_q(img->codec_context->framerate);
video_stream->time_base = img->codec_context->time_base;
if (img->video_format_context->oformat->flags & AVFMT_GLOBALHEADER)
img->codec_context->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
/* Some codecs require the CRF value */
if (codec_id == AV_CODEC_ID_H264 || codec_id == AV_CODEC_ID_H265)
{
gchar *crf = g_strdup_printf("%i", bitrate_crf);
av_opt_set(img->codec_context->priv_data, "crf", crf, AV_OPT_SEARCH_CHILDREN);
g_free(crf);
}
/* Set exporting stage to be multithreaded */
AVDictionary* opts = NULL;
av_dict_set(&opts, "threads", "auto", 0);
/* Open video encoder */
ret = avcodec_open2(img->codec_context, vcodec, &opts);
if (ret < 0)
{
img_message(img, TRUE, _("Failed to open the video encoder\n"));
return FALSE;
}
/* Copy video encoder parameters to output stream */
ret = avcodec_parameters_from_context(video_stream->codecpar, img->codec_context);
if (ret < 0)
{
img_message(img, TRUE, _("Failed to copy video encoder parameters to output stream\n"));
return FALSE;
}
/* AVFRAME stuff */
img->video_frame = av_frame_alloc();
img->video_frame->format = AV_PIX_FMT_RGBA;
img->video_frame->width = img->video_size[0];
img->video_frame->height = img->video_size[1];
av_frame_make_writable(img->video_frame);
ret = av_frame_get_buffer(img->video_frame, 1);
if (ret < 0)
img_message(img,TRUE, _("Could not allocate the video frame data\n"));
img->video_packet = av_packet_alloc();
And here I called repeatedly (the function is called somewehere else) av_send_frame() but it throws the error in the subject:
gint width, height, stride, row, col, offset;
uint8_t *pix;
/* Image info and pixel data */
width = cairo_image_surface_get_width( surface );
height = cairo_image_surface_get_height( surface );
stride = cairo_image_surface_get_stride( surface );
pix = cairo_image_surface_get_data( surface );
for( row = 0; row < height; row++ )
{
for( col = 0; col < width; col++ )
{
offset = 3 * col + row * img->video_frame->linesize[0];
img->video_frame->data[0][offset + 0] = pix[0];
img->video_frame->data[0][offset + 1] = pix[1];
img->video_frame->data[0][offset + 2] = pix[2];
}
}
img_export_encode_av_frame(img->video_frame, img->video_format_context, img->codec_context, img->video_packet);
return TRUE;
}
void img_export_encode_av_frame(AVFrame *frame, AVFormatContext *fmt, AVCodecContext *ctx, AVPacket *pkt)
{
gint ret;
/* send the frame to the encoder */
ret = avcodec_send_frame(ctx, frame);
if (ret < 0)
g_print("Error sending a frame for encoding\n");
while (ret >= 0)
{
ret = avcodec_receive_packet(ctx, pkt);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0)
g_print("Error during encoding\n");
av_interleaved_write_frame(fmt, pkt);
av_packet_unref(pkt);
}
}
I googled here also but with no luck. It seems I'm the only one to encode a cairo surface. Grepping the error message in ffmpeg sources didn't help. How do I set the stride? I read ffmpeg does it for me once I allocate the buffer for the frame but in my case it seems it doesn't. Where am I wrong?