[FFmpeg-devel] Fwd: framebuffer device demuxer

Måns Rullgård mans
Fri Jan 28 17:32:38 CET 2011


Stefano Sabatini <stefano.sabatini-lala at poste.it> writes:

> On date Friday 2011-01-28 01:10:46 +0000, M?ns Rullg?rd encoded:
>
>> I think "framebuffer" is a bit too generic a name.  After all,
>> anything with a display of any kind has a framebuffer.  The Linux
>> framebuffer device generally goes by the name "fbdev", so perhaps that
>> would be a better name.
>
> Replaced with linuxfb, this should be more explicative of the fact
> that it is a linux thing, this should prevent having users ask "I'm on
> windows, why can't I find the fbdev device?".

Works for me.

>> > +    if ((fb->fd = open(avctx->filename, flags)) == -1) {
>> > +        ret = AVERROR(errno);
>> > +        av_log(avctx, AV_LOG_ERROR, "Could not open framebuffer device '%s'.\n", avctx->filename);
>> > +        goto fail;
>> 
>> You could return directly here and drop the check before close().
>
> Done.

Not exactly...

>> > +    fb->width  = fb_varinfo.xres;
>> > +    fb->height = fb_varinfo.yres;
>> > +    bits_per_pixel = fb_varinfo.bits_per_pixel;
>> > +
>> > +    switch (bits_per_pixel) {
>> > +    case  8: pix_fmt = PIX_FMT_PAL8  ; break;
>> > +    case 15: pix_fmt = PIX_FMT_BGR555; break;
>> > +    case 16: pix_fmt = PIX_FMT_RGB565; break;
>> > +    case 24: pix_fmt = PIX_FMT_RGB24 ; break;
>> > +    case 32: pix_fmt = PIX_FMT_RGB32 ; break;
>> > +    default:
>> > +        ret = AVERROR(EINVAL);
>> > +        av_log(avctx, AV_LOG_ERROR, "Image with bits per pixel depth %d not supported.\n",
>> > +               bits_per_pixel);
>> > +        goto fail;
>> > +    }
>> 
>> These are not the only formats possible.  You cannot use bits per
>> pixel exclusively to determine the format.
>
> Yes indeed. I'm using a far more robust solution now, yet incomplete,
> also I have to see how to handle pal formats.

There is also the issue of driver-specific formats, but let's ignore
those for now.

>> > +AVInputFormat framebuffer_demuxer = {
>> > +    .name           = "framebuffer",
>> > +    .long_name      = NULL_IF_CONFIG_SMALL("Linux framebuffer"),
>> > +    .priv_data_size = sizeof(FrameBufferContext),
>> > +    .read_header    = framebuffer_read_header,
>> > +    .read_packet    = framebuffer_read_packet,
>> > +    .read_close     = framebuffer_read_close,
>> > +    .flags          = AVFMT_NOFILE,
>> > +};
>> 
>> Is AVFMT_NOFILE really correct here?  I'm not sure what its semantics
>> are supposed to be.
>
> It's not explained in the docs, but AVFMT_NOFILE is used for all the
> input and output device (possibly is what distinguishes a device from
> a muxer/demuxer).

OK, that's a reasonable explanation.  Perhaps it should be documented
somewhere.

> And I'm still observing the 100% CPU problem noted by Luca A. in this
> thread,

That needs to be resolved, obviously.

> a 0-memcpy solution is possible but it requires some change to the
> framework (as the written packet contains aligned data, which is not
> supported ATM).

I don't think a zero-copy is a good idea here.  The framebuffer is
likely to be updated while encoding is in progress.

> @@ -2863,6 +2864,33 @@ fi
>  
>  texi2html -version > /dev/null 2>&1 && enable texi2html || disable texi2html
>  
> +if enabled network; then
> +    check_type "sys/types.h sys/socket.h" socklen_t
> +    check_type netdb.h "struct addrinfo"
> +    check_type netinet/in.h "struct ipv6_mreq" -D_DARWIN_C_SOURCE
> +    check_type netinet/in.h "struct sockaddr_in6"
> +    check_type "sys/types.h sys/socket.h" "struct sockaddr_storage"
> +    check_struct "sys/types.h sys/socket.h" "struct sockaddr" sa_len
> +    # Prefer arpa/inet.h over winsock2
> +    if check_header arpa/inet.h ; then
> +        check_func closesocket
> +    elif check_header winsock2.h ; then
> +        check_func_headers winsock2.h closesocket -lws2 && \
> +            network_extralibs="-lws2" || \
> +        { check_func_headers winsock2.h closesocket -lws2_32 && \
> +            network_extralibs="-lws2_32"; }
> +        check_type ws2tcpip.h socklen_t
> +        check_type ws2tcpip.h "struct addrinfo"
> +        check_type ws2tcpip.h "struct ipv6_mreq"
> +        check_type ws2tcpip.h "struct sockaddr_in6"
> +        check_type ws2tcpip.h "struct sockaddr_storage"
> +        check_struct winsock2.h "struct sockaddr" sa_len
> +    else
> +        disable network
> +    fi
> +fi

Bad merge?  This chunk was moved up a while ago.

> +check_header linux/fb.h
>  check_header linux/videodev.h
>  check_header linux/videodev2.h
>  check_header sys/videoio.h

[...]

> diff --git a/libavdevice/linuxfb.c b/libavdevice/linuxfb.c
> new file mode 100644
> index 0000000..e174edf
> --- /dev/null
> +++ b/libavdevice/linuxfb.c
> @@ -0,0 +1,234 @@
> +/*
> + * Copyright (c) 2010 Stefano Sabatini
> + * Copyright (c) 2009 Giliard B. de Freitas <giliarde at gmail.com>
> + * Copyright (C) 2002 Gunnar Monell <gmo at linux.nu>
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/**
> + * @file
> + * Linux framebuffer input device,
> + * inspired by code from fbgrab.c by Gunnar Monell.
> + */
> +
> +#include <unistd.h>
> +#include <fcntl.h>
> +#include <sys/ioctl.h>
> +#include <sys/time.h>
> +#include <sys/mman.h>
> +#include <time.h>
> +#include <linux/fb.h>
> +
> +#include "libavutil/mem.h"
> +#include "libavutil/pixdesc.h"
> +#include "libavformat/avformat.h"
> +
> +struct rgb_pixfmt_map_entry {
> +    int bits_per_pixel;
> +    int red_offset, green_offset, blue_offset, alpha_offset;
> +    enum PixelFormat pixfmt;
> +};
> +
> +static struct rgb_pixfmt_map_entry rgb_pixfmt_map[] = {
> +    // bpp, r_offset,  g_offset, b_offset, a_offset, pixfmt
> +    {  32,   0,         8,       16,       24,       PIX_FMT_RGBA  },
> +    {  32,  16,         8,        0,       24,       PIX_FMT_BGRA  },
> +    {  32,   8,        16,       24,        0,       PIX_FMT_ARGB  },
> +    {  32,   3,         2,        8,        0,       PIX_FMT_ABGR  },
> +    {  24,   0,         8,       16,        0,       PIX_FMT_RGB24 },
> +    {  24,  16,         8,        0,        0,       PIX_FMT_BGR24 },
> +};
> +
> +static enum PixelFormat get_pixfmt_from_fb_varinfo(struct fb_var_screeninfo varinfo)

Please change the argument to a pointer.

> +{
> +    int i;
> +
> +    for (i = 0; i < FF_ARRAY_ELEMS(rgb_pixfmt_map); i++) {
> +        struct rgb_pixfmt_map_entry entry = rgb_pixfmt_map[i];

Please use a pointer here.

> +        if (entry.bits_per_pixel == varinfo.bits_per_pixel &&
> +            entry.red_offset     == varinfo.red.offset     &&
> +            entry.green_offset   == varinfo.green.offset   &&
> +            entry.blue_offset    == varinfo.blue.offset)
> +            return entry.pixfmt;
> +    }
> +
> +    return PIX_FMT_NONE;
> +}
> +
> +typedef struct {
> +    int frame_size;          ///< size in bytes of a grabbed frame
> +    AVRational time_base;    ///< time base
> +    int64_t time_frame;      ///< current time
> +
> +    int frame_linesize;      ///< linesize of the output frame
> +    int linesize;            ///< linesize of the read framebuffer
> +    int height;              ///< height of the grab frame
> +    int width;               ///< width of the grab frame
> +    int fd;                  ///< framebuffer device file descriptor
> +
> +    uint8_t *data;           ///< framebuffer data
> +    uint8_t *visible_data;   ///< framebuffer visible data
> +} FrameBufferContext;
> +
> +av_cold static int linuxfb_read_header(AVFormatContext *avctx, AVFormatParameters *ap)
> +{
> +    FrameBufferContext *fb = avctx->priv_data;
> +    struct fb_var_screeninfo fb_varinfo;
> +    struct fb_fix_screeninfo fb_fixinfo;
> +    AVStream *st = NULL;
> +    enum PixelFormat pix_fmt;
> +    int ret, bytes_per_pixel, flags = O_RDONLY;
> +
> +    if (!(st = av_new_stream(avctx, 0)))
> +        return AVERROR(ENOMEM);
> +
> +    if (avctx->flags & AVFMT_FLAG_NONBLOCK)
> +        flags |= O_NONBLOCK;
> +
> +    if ((fb->fd = open(avctx->filename, flags)) == -1) {
> +        ret = AVERROR(errno);
> +        av_log(avctx, AV_LOG_ERROR, "Could not open framebuffer device '%s': %s\n",
> +               avctx->filename, strerror(ret));
> +        close(fb->fd);

Err... that should be "return ret", not close().

> +    }
> +
> +    if (ioctl(fb->fd, FBIOGET_VSCREENINFO, &fb_varinfo) < 0) {
> +        ret = AVERROR(errno);
> +        av_log(avctx, AV_LOG_ERROR, "FBIOGET_VSCREENINFO: %s\n", strerror(errno));
> +        goto fail;
> +    }
> +
> +    if (ioctl(fb->fd, FBIOGET_FSCREENINFO, &fb_fixinfo) < 0) {
> +        ret = AVERROR(errno);
> +        av_log(avctx, AV_LOG_ERROR, "FBIOGET_FSCREENINFO: %s\n", strerror(errno));
> +        goto fail;
> +    }
> +
> +    if (ap->time_base.den <= 0) {
> +        ret = AVERROR(EINVAL);
> +        av_log(avctx, AV_LOG_ERROR, "Invalid time base %d/%d\n", ap->time_base.num, ap->time_base.den);
> +        goto fail;
> +    }
> +
> +    av_set_pts_info(st, 64, 1, 1000000); /* 64 bits pts in microseconds */
> +
> +    fb->width  = fb_varinfo.xres;
> +    fb->height = fb_varinfo.yres;
> +
> +    pix_fmt = get_pixfmt_from_fb_varinfo(fb_varinfo);
> +    if (pix_fmt == PIX_FMT_NONE) {
> +        ret = AVERROR(EINVAL);
> +        av_log(avctx, AV_LOG_ERROR, "Image with bits per pixel depth %d not supported.\n",
> +               fb_varinfo.bits_per_pixel);

This error message doesn't quite match the error condition.  I'd go
with something like "Framebuffer pixel format not supported".

> +        goto fail;
> +    }
> +
> +    bytes_per_pixel    = (fb_varinfo.bits_per_pixel + 7) >> 3;
> +    fb->frame_linesize = fb_varinfo.xres * bytes_per_pixel;
> +    fb->frame_size     = fb->frame_linesize * fb_varinfo.yres;
> +    fb->linesize       = fb_fixinfo.line_length;
> +    fb->time_base      = ap->time_base;
> +    fb->time_frame     = av_gettime() / av_q2d(ap->time_base);

Don't initialise time_frame to current time.  There could be any delay
between init and first capture.  Set it to something invalid instead,
and check it in read_packet().

> +    fb->data = mmap(NULL, fb_fixinfo.line_length * (fb_varinfo.yres + fb_varinfo.yoffset),
> +                    PROT_READ, MAP_SHARED, fb->fd, 0);
> +    fb->visible_data = fb->data +
> +        (fb_varinfo.xoffset + fb_varinfo.xres_virtual * fb_varinfo.yoffset) * bytes_per_pixel;

This can change at any time if an application reconfigures the
framebuffer.  I'm not sure, but I think this also happens
automatically when the text console scrolls.

> +    if (fb->data == MAP_FAILED) {
> +        ret = AVERROR(errno);
> +        av_log(avctx, AV_LOG_ERROR, "Error in mmap(): %s\n", strerror(errno));
> +        goto fail;
> +    }
> +
> +    st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
> +    st->codec->codec_id   = CODEC_ID_RAWVIDEO;
> +    st->codec->width      = fb->width;
> +    st->codec->height     = fb->height;
> +    st->codec->pix_fmt    = pix_fmt;
> +    st->codec->time_base  = ap->time_base;
> +    st->codec->bit_rate   = fb->frame_size / av_q2d(ap->time_base) * 8;
> +
> +    av_log(avctx, AV_LOG_INFO, "w:%d h:%d bpp:%d pixfmt:%s tb:%d/%d bit_rate:%d\n",
> +           fb->width, fb->height, fb_varinfo.bits_per_pixel,
> +           av_pix_fmt_descriptors[pix_fmt].name, ap->time_base.num, ap->time_base.den,
> +           st->codec->bit_rate);
> +    return 0;
> +
> +fail:
> +    if (fb->fd >= 0)
> +        close(fb->fd);

Fix the open() check above and remove this if().

> +    return ret;
> +}
> +
> +static int linuxfb_read_packet(AVFormatContext *avctx, AVPacket *pkt)
> +{
> +    FrameBufferContext *fb = avctx->priv_data;
> +    int64_t curtime, delay;
> +    struct timespec ts;
> +    int i, ret;
> +    uint8_t *pin, *pout;
> +
> +    /* wait based on the frame rate */
> +    while (1) {
> +        curtime = av_gettime();
> +        delay = curtime - fb->time_frame * av_q2d(fb->time_base);
> +        if (delay >= 0) {
> +            fb->time_frame += INT64_C(1000000) * av_q2d(fb->time_base);
> +            break;
> +        }
> +        if (avctx->flags & AVFMT_FLAG_NONBLOCK)
> +            return AVERROR(EAGAIN);
> +        ts.tv_sec  =  delay / 1000000;
> +        ts.tv_nsec = (delay % 1000000) * 1000;
> +        nanosleep(&ts, NULL);

This is asking for a negative delay.  That's probably the cause of the
CPU hogging.

> +    }
> +
> +    if ((ret = av_new_packet(pkt, fb->frame_size)) < 0)
> +        return ret;
> +
> +    pkt->pts = curtime;
> +    pin  = fb->visible_data;
> +    pout = pkt->data;
> +
> +    for (i = 0; i < fb->height; i++) {
> +        memcpy(pout, pin, fb->frame_linesize);
> +        pin  += fb->linesize;
> +        pout += fb->frame_linesize;
> +    }
> +
> +    return fb->frame_size;
> +}
> +
> +av_cold static int linuxfb_read_close(AVFormatContext *avctx)
> +{
> +    FrameBufferContext *fb = avctx->priv_data;
> +
> +    munmap(fb->data, fb->frame_size);
> +    close(fb->fd);
> +
> +    return 0;
> +}
> +
> +AVInputFormat ff_linuxfb_demuxer = {
> +    .name           = "linuxfb",
> +    .long_name      = NULL_IF_CONFIG_SMALL("Linux framebuffer"),
> +    .priv_data_size = sizeof(FrameBufferContext),
> +    .read_header    = linuxfb_read_header,
> +    .read_packet    = linuxfb_read_packet,
> +    .read_close     = linuxfb_read_close,
> +    .flags          = AVFMT_NOFILE,
> +};
> -- 
> 1.7.2.3
>
>

-- 
M?ns Rullg?rd
mans at mansr.com



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