[Libav-user] Fill AVFrame from a Cairo surface

[Paul B Mahol]

On Wed, Aug 18, 2021 at 1:17 PM Colossus <colossus73 at gmail.com> wrote:

> Ok, I reordered the code. I don't get anymore the annoying message
> 'input picture width greater than stride' but I get a crash in memalloc()
> called
> by av_send_frame().
>
> *This is the gdb output:*
> Thread 1 "imagination" received signal SIGABRT, Aborted.
> __GI_raise (sig=sig at entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
> 50 ../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
> (gdb) bt
> #0  __GI_raise (sig=sig at entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
> #1  0x00007ffff5518537 in __GI_abort () at abort.c:79
> #2  0x00007ffff5571768 in __libc_message (action=action at entry=do_abort,
> fmt=fmt at entry=0x7ffff567fe2d "%s\n")
>     at ../sysdeps/posix/libc_fatal.c:155
> #3  0x00007ffff5578a5a in malloc_printerr (str=str at entry=0x7ffff5682110
> "malloc_consolidate(): invalid chunk size")
>     at malloc.c:5347
> #4  0x00007ffff5579918 in malloc_consolidate (av=av at entry=0x7ffff56b1b80
> <main_arena>) at malloc.c:4477
> #5  0x00007ffff557b755 in _int_malloc (av=av at entry=0x7ffff56b1b80
> <main_arena>, bytes=bytes at entry=16288) at malloc.c:3699
> #6  0x00007ffff557c4af in _int_memalign
>     (av=av at entry=0x7ffff56b1b80 <main_arena>, alignment=alignment at entry=64,
> bytes=bytes at entry=16176) at malloc.c:4684
> #7  0x00007ffff557d55c in _mid_memalign (alignment=64, bytes=16176,
> address=<optimized out>) at malloc.c:3312
> #8  0x00007ffff1e9fb2a in x264_malloc () at
> /lib/x86_64-linux-gnu/libx264.so.160
> #9  0x00007ffff1eba75c in  () at /lib/x86_64-linux-gnu/libx264.so.160
> #10 0x00007ffff1ebe6b0 in  () at /lib/x86_64-linux-gnu/libx264.so.160
> #11 0x00007ffff1f27957 in  () at /lib/x86_64-linux-gnu/libx264.so.160
> #12 0x00007ffff1ea4aa1 in x264_encoder_encode () at
> /lib/x86_64-linux-gnu/libx264.so.160
> #13 0x00007ffff62df6d8 in  () at /lib/x86_64-linux-gnu/libavcodec.so.58
> #14 0x00007ffff6094c37 in avcodec_encode_video2 () at
> /lib/x86_64-linux-gnu/libavcodec.so.58
> #15 0x00007ffff6095012 in  () at /lib/x86_64-linux-gnu/libavcodec.so.58
> #16 0x00007ffff609519f in *avcodec_send_frame* () at
> /lib/x86_64-linux-gnu/libavcodec.so.58
> #17 0x000055555557aaae in img_export_encode_av_frame
>     (pkt=0x5555556e6d60, ctx=0x55555643cb40, fmt=0x5555564859c0,
> frame=<optimized out>) at export.c:968
>
> And this is the code:
> static gboolean img_export_frame_to_avframe(img_window_struct *img,
> cairo_surface_t *surface)
> {
> static gint i = 0;
>
> gint width, height, stride, row, col, offset, ret;
> uint8_t  *pix, *data;
> AVFrame *frame;
>
> /* 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 );
>
> /* Initialize AVFrame to be sent to the encoder */
> frame = av_frame_alloc();
> frame->format = img->codec_context->pix_fmt;
> frame->width  = img->video_size[0];
> frame->height = img->video_size[1];
> av_frame_get_buffer(frame, 32);
>

Why 32?, in doxy 0 is recommended, unless programmer know exactly what he
is doing.


>      /* Fill the frame data with pixels from the Cairo surface */
> for( row = 0; row < height; row++ )
> {
> data = pix + row * stride;
> for( col = 0; col < width; col++ )
> {
> frame->data[0][row * frame->linesize[0] + col] = data[2];
> frame->data[1][row * frame->linesize[1] + col] = data[1];
> frame->data[2][row * frame->linesize[2] + col] = data[0];
> data += 4;
> }
> frame->pts = i;
> i++;
> }
> //sws_scale(img->sws_ctx, pix, img->video_frame->linesize, 0,
> img->video_frame->height, img->video_frame->data, sws_frame->linesize);
>
> ret = img_export_encode_av_frame(frame, img->video_format_context,
> img->codec_context, &img->video_packet);
>
> if (frame)
> {
> av_frame_free(&frame);
> frame = NULL;
> }
> return ret;
> }
>
> gboolean 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("Av error: %s\n",av_err2str(ret));
> g_print("Error sending a frame for encoding\n");
> return FALSE;
> }
>     while (ret >= 0)
>     {
>         ret = avcodec_receive_packet(ctx, pkt);
>         if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
> return TRUE;
>         else if (ret < 0)
> g_print("Error during encoding\n");
>
> av_interleaved_write_frame(fmt, pkt);
> av_packet_unref(pkt);
> return FALSE;
>     }
>     return TRUE;
> }
>
> What can be the cause of the crash now?
>

Check with valgrind or similar for buffer overreads or overwrites.


>
> Thanks
>
> On Mon, 16 Aug 2021 at 16:35, Nicolas George <george at nsup.org> wrote:
>
>> Colossus (12021-08-16):
>> > I told you I did and avcodec_send_frame() is the one that throws that
>> error.
>>
>> I will trust the code I see. Re-post your code once you have fixed the
>> order of the function calls and checked all the return values properly,
>> if it still does not work.
>>
>> --
>>   Nicolas George
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