[FFmpeg-devel] Fwd: framebuffer device demuxer
Måns Rullgård
mans
Fri Jan 28 02:10:46 CET 2011
Sorry to chip in so late, but here are some comments on this, mostly
minor.
Stefano Sabatini <stefano.sabatini-lala at poste.it> writes:
> From 9059a39f16131efc768d59784bd0179a2dfce69d Mon Sep 17 00:00:00 2001
> From: Stefano Sabatini <stefano.sabatini-lala at poste.it>
> Date: Tue, 25 Jan 2011 19:40:29 +0100
> Subject: [PATCH] Add Linux framebuffer device.
>
> Based on a patch by Giliard B. de Freitas /com/gmail/giliarde.
>
> See thread:
> Subject: [FFmpeg-devel] Fwd: framebuffer device demuxer
> Date: Sat, 23 May 2009 09:32:13 -0300
> ---
> Changelog | 1 +
> configure | 2 +
> doc/indevs.texi | 18 ++++
> libavdevice/Makefile | 1 +
> libavdevice/alldevices.c | 1 +
> libavdevice/framebuffer.c | 216 +++++++++++++++++++++++++++++++++++++++++++++
> 6 files changed, 239 insertions(+), 0 deletions(-)
> create mode 100644 libavdevice/framebuffer.c
>
> diff --git a/Changelog b/Changelog
> index 8b7efb6..1c9166e 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -74,6 +74,7 @@ version <next>:
> - Lagarith decoder
> - ffmpeg -copytb option added
> - IVF muxer added
> +- Linux framebuffer input device added
>
>
> version 0.6:
> diff --git a/configure b/configure
> index 001f00a..e75ad41 100755
> --- a/configure
> +++ b/configure
> @@ -1387,6 +1387,7 @@ alsa_indev_deps="alsa_asoundlib_h snd_pcm_htimestamp"
> alsa_outdev_deps="alsa_asoundlib_h"
> bktr_indev_deps_any="dev_bktr_ioctl_bt848_h machine_ioctl_bt848_h dev_video_bktr_ioctl_bt848_h dev_ic_bt8xx_h"
> dv1394_indev_deps="dv1394 dv_demuxer"
> +framebuffer_indev_deps="linux_fb_h"
> jack_indev_deps="jack_jack_h"
> libdc1394_indev_deps="libdc1394"
> oss_indev_deps_any="soundcard_h sys_soundcard_h"
> @@ -2848,6 +2849,7 @@ if enabled network; then
> fi
> fi
>
> +check_header linux/fb.h
> check_header linux/videodev.h
> check_header linux/videodev2.h
> check_header sys/videoio.h
> diff --git a/doc/indevs.texi b/doc/indevs.texi
> index 8e862ff..e9b1bea 100644
> --- a/doc/indevs.texi
> +++ b/doc/indevs.texi
> @@ -59,6 +59,24 @@ BSD video input device.
>
> Linux DV 1394 input device.
>
> + at section framebuffer
> +
> +Linux framebuffer input device.
> +
> +The name of the framebuffer device to read is a file device node,
> +usually @file{/dev/fb0}.
> +
> +For example, to record from the framebuffer device /dev/fb0 with
> + at file{ffmpeg}:
> + at example
> +ffmpeg -f framebuffer -r 10 -i /dev/fb0 out.avi
> + at end example
> +
> +You can take a single screenshot image with the command:
> + at example
> +ffmpeg -f framebuffer -vframes 1 -r 1 -i /dev/fb0 screenshot.jpeg
> + at end example
> +
> @section jack
>
> JACK input device.
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.
> diff --git a/libavdevice/Makefile b/libavdevice/Makefile
> index 1c0630b..f5afeb2 100644
> --- a/libavdevice/Makefile
> +++ b/libavdevice/Makefile
> @@ -14,6 +14,7 @@ OBJS-$(CONFIG_ALSA_OUTDEV) += alsa-audio-common.o \
> alsa-audio-enc.o
> OBJS-$(CONFIG_BKTR_INDEV) += bktr.o
> OBJS-$(CONFIG_DV1394_INDEV) += dv1394.o
> +OBJS-$(CONFIG_FRAMEBUFFER_INDEV) += framebuffer.o
> OBJS-$(CONFIG_JACK_INDEV) += jack_audio.o
> OBJS-$(CONFIG_OSS_INDEV) += oss_audio.o
> OBJS-$(CONFIG_OSS_OUTDEV) += oss_audio.o
> diff --git a/libavdevice/alldevices.c b/libavdevice/alldevices.c
> index de3bc82..4e79467 100644
> --- a/libavdevice/alldevices.c
> +++ b/libavdevice/alldevices.c
> @@ -42,6 +42,7 @@ void avdevice_register_all(void)
> REGISTER_INOUTDEV (ALSA, alsa);
> REGISTER_INDEV (BKTR, bktr);
> REGISTER_INDEV (DV1394, dv1394);
> + REGISTER_INDEV (FRAMEBUFFER, framebuffer);
> REGISTER_INDEV (JACK, jack);
> REGISTER_INOUTDEV (OSS, oss);
> REGISTER_INDEV (V4L2, v4l2);
> diff --git a/libavdevice/framebuffer.c b/libavdevice/framebuffer.c
> new file mode 100644
> index 0000000..65ebe5c
> --- /dev/null
> +++ b/libavdevice/framebuffer.c
> @@ -0,0 +1,216 @@
> +/*
> + * 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"
> +
> +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; ///< image data
> +} FrameBufferContext;
> +
> +/**
> + * Initialize the framebuffer input device.
> + */
> +av_cold static int framebuffer_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, bits_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'.\n", avctx->filename);
> + goto fail;
You could return directly here and drop the check before 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;
> + 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.
> + fb->frame_linesize = fb_varinfo.xres * ((bits_per_pixel + 7) >> 3);
> + 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);
> + fb->data = mmap(NULL, fb_fixinfo.line_length * fb_varinfo.yres,
> + PROT_READ, MAP_SHARED, fb->fd, 0);
> + 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, 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);
> + return ret;
> +}
> +
> +/**
> + * Grab a frame from the frame buffer device.
> + *
> + * @param pkt packet holding the grabbed frame
> + * @return frame size in bytes
> + */
> +static int framebuffer_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);
> + }
Using e.g. sem_timedwait(), which takes an absolute timeout, might
give better accuracy here, at least on the off-chance that the process
is descheduled between the av_gettime() and nanosleep() calls.
> + if ((ret = av_new_packet(pkt, fb->frame_size)) < 0)
> + return ret;
> +
> + pkt->pts = curtime;
> + pin = fb->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;
> +}
> +
> +/**
> + * Close framebuffer input device.
> + *
> + * @return a negative value in case of errors, 0 otherwise
This comment is a lie. The function always returns 0. Not that much
could go wrong...
> + */
> +av_cold static int framebuffer_read_close(AVFormatContext *avctx)
> +{
> + FrameBufferContext *fb = avctx->priv_data;
> +
> + munmap(fb->data, fb->frame_size);
> + close(fb->fd);
> +
> + return 0;
> +}
> +
> +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.
--
M?ns Rullg?rd
mans at mansr.com
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