[FFmpeg-devel] [PATCH] VFW capture support
Zuxy Meng
zuxy.meng
Mon Mar 3 08:10:57 CET 2008
Hi,
2008/3/3, M?ns Rullg?rd <mans at mansr.com>:
> Ramiro Polla <ramiro at lisha.ufsc.br> writes:
>
> > Hello,
> >
> > M?ns Rullg?rd wrote:
> > [...]
> >>> - I tried to make the code look as much as possible as the code given
> >>> in MSDN, so that means I used "LRESULT CALLBACK" without even knowing
> >>> what it does or if it can be removed.
> >> I'm afraid that's unacceptable in FFmpeg. Please find out what it
> >> does.
> >
> > CALLBACK changed to __stdcall.
>
> OK, I see what it does, and it should be left as CALLBACK, in case
> it's not always defined to __stdcall.
Absolutely. There's no __stdcall in Windows x64.
>
> >>> I have also used "var == FALSE" and "var == NULL" checks. I prefer
> >>> that instead of "!var" just to be closer to MSDN.
> >> Using "var == FALSE", and "var == TRUE" more so, not only not our
> >> style, it's plain stupid. Being closer to msdn is hardly a desirable
> >> goal.
> >
> > Hey, we never know if Microsoft someday decides that FALSE == 18
> > instead of the expected 0...
>
> Fair point.
>
> > You even say it yourself a few lines down from here:
> >> Are these values guaranteed to be correct for all Windows versions?
> >
> > Anyways, I don't really care that much: changed.
> >
> >>> - Some defines are missing from MinGW include headers. I'll try to get
> >>> them integrated into MinGW. After that, we can properly check for
> >>> MinGW versions to define them, or just plain remove the definitions
> >>> here and require a newer version of MinGW. In the meantime, I think
> >>> there's no problem in defining them here.
> >> Are these values guaranteed to be correct for all Windows versions?
> >
> > Probably. If it's not correct, we'll know as soon as someone submits a
> > bug report or a patch.
>
> I guess it's acceptable, even if I don't like it. Then again, I don't
> like the idea of Windows in the first place.
>
> >>> - If no "-r" parameter is given, way too many frames are read. I
> >>> thought FFmpeg was supposed to read the first few frames and decide
> >>> the rate based on that. The capture blocks, so the timestamps are
> >>> correct, and if some frames were captured and then the frame rate
> >>> calculated, it should find the correct frame rate, right?
> >> FFmpeg does not estimate frame rate based on elapsed real time,
> >> AFAIK.
> >
> > The question is if it estimates frame rate based on pts. Real time or
> > not is irrelevant here.
>
> Of course you're right. I don't know what I was thinking. That said,
> can't you set the frame rate in read_header()?
>
> >>> Please review.
> >> I am shocked an appalled by the ugly casting required by the win32
> >> API, but there's of course nothing we can do about that.
> >
> > Please refrain from your predictable Windows bashing in the subsequent
> > reviews. Thank you.
>
> I'll bash it all I want. It'll still be getting far less than it
> deserves.
>
> >>> struct vfw_ctx {
> >>> HWND hwnd;
> >>> int grabbed;
> >>> AVPacket *pkt;
> >>> };
> >>>
> >>> static int vfw_pixfmt( DWORD biCompression )
> >> Do we really have to use those dreadful windows typedefs and naming
> >> conventions?
> >
> > I find it best when writing an interface to an API that has
> > documentation, the same way you follow variable names from specs.
>
> This function isn't part of any API.
>
> >> It is preferred to have no whitespace immediately inside () in FFmpeg.
> >
> > This is my preferred style, and I'll maintain this file. You won't
> > need to look at it after it gets into SVN.
>
> FFmpeg should use a consistent style.
>
> >>> {
> >>> switch( biCompression ) {
> >>> case MKTAG( 'Y', 'U', 'Y', '2' ):
> >>> return PIX_FMT_YUYV422;
> >>> default:
> >>> return PIX_FMT_BGR24;
> >>> }
> >> Is this really complete and correct?
> >
> > Complete? Most likely not.
> > Correct? For me it is...
>
> I'm quite suspicious about the default case. Would it not be better
> to list the known values explicitly, and report an error for unknown
> values.
>
> > We'll know more as users submit the output from
> > ffmpeg -f vfwcap -i 0 -v 99
> >
> >>> }
> >>>
> >>> static void dump_bih( AVFormatContext *s, BITMAPINFO *bih )
> >>> {
> >>> av_log( s, AV_LOG_DEBUG, " biSize:\t%d\n", (int) bih->bmiHeader.biSize );
> >>> av_log( s, AV_LOG_DEBUG, " biWidth:\t%d\n", (int) bih->bmiHeader.biWidth );
> >>> av_log( s, AV_LOG_DEBUG, " biHeight:\t%d\n", (int) bih->bmiHeader.biHeight );
> >>> av_log( s, AV_LOG_DEBUG, " biPlanes:\t%d\n", (int) bih->bmiHeader.biPlanes );
> >>> av_log( s, AV_LOG_DEBUG, " biBitCount:\t%d\n", (int) bih->bmiHeader.biBitCount );
> >>> av_log( s, AV_LOG_DEBUG, " biCompression:\t%.4s\n", (char*) &bih->bmiHeader.biCompression );
> >>> av_log( s, AV_LOG_DEBUG, " biSizeImage:\t%d\n", (int) bih->bmiHeader.biSizeImage );
> >>> av_log( s, AV_LOG_DEBUG, " biXPelsPerMeter:\t%d\n", (int) bih->bmiHeader.biXPelsPerMeter );
> >>> av_log( s, AV_LOG_DEBUG, " biYPelsPerMeter:\t%d\n", (int) bih->bmiHeader.biYPelsPerMeter );
> >>> av_log( s, AV_LOG_DEBUG, " biClrUsed:\t%d\n", (int) bih->bmiHeader.biClrUsed );
> >>> av_log( s, AV_LOG_DEBUG, " biClrImportant:\t%d\n", (int) bih->bmiHeader.biClrImportant );
> >> All those (int) casts are unnecessary.
> >
> > warning: format '%d' expects type 'int', but argument 4 has type 'DWORD'
>
> That's because DWORD is 'unsigned long' (at least on 32-bit), so the
> format specifier should be %lu.
>
> >> If any of the fields are
> >> unsigned, the corresponding format specifiers should be %u.
> >
> > http://msdn2.microsoft.com/en-us/library/ms532290(VS.85).aspx
> > They're defined as DWORDs and LONGs. Some allow negative numbers, the
> > rest I don't know but have never seen with signed numbers.
> > It's just debugging information. We'll learn more with bug reports.
>
> DWORD is unsigned, and so should use an unsigned format specifier.
> Debugging being correct is as important as anything.
>
> > [more predictable Windows bashing]
> >
> > [Useless (LRESULT) casts]
> >
> > Removed.
> >
> >>> pkt->pts = GetTickCount( );
> >>> memcpy( pkt->data, vdhdr->lpData, vdhdr->dwBytesUsed );
> >> Is it really not possible to capture without this memcpy()?
> >
> > That's the best I found. The suggested way of capturing VFW frames
> > from MSDN involves copying to the clipboard and then to whatever you
> > need it for. Maybe someday someone will find some dirty hack that
> > avoids it.
>
> Video... clipboard... words do not exist to express my disgust.
>
> > /*
> > * VFW capture interface
> > * Copyright (c) 2006-2008 Ramiro Polla.
> > *
> > * 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
> > */
> >
> > #include "avformat.h"
> > #include <vfw.h>
> > #include <windows.h>
> >
> > /* Defines for VFW missing from MinGW.
> > * Remove this when MinGW incorporates them. */
> > #define WM_CAP_START (0x0400)
> > #define WM_CAP_SET_CALLBACK_FRAME (WM_CAP_START + 5)
> > #define WM_CAP_GET_USER_DATA (WM_CAP_START + 8)
> > #define WM_CAP_SET_USER_DATA (WM_CAP_START + 9)
> > #define WM_CAP_DRIVER_CONNECT (WM_CAP_START + 10)
> > #define WM_CAP_DRIVER_DISCONNECT (WM_CAP_START + 11)
> > #define WM_CAP_GRAB_FRAME (WM_CAP_START + 60)
> > #define WM_CAP_GET_VIDEOFORMAT (WM_CAP_START + 44)
> > #define WM_CAP_SET_PREVIEW (WM_CAP_START + 50)
> > #define WM_CAP_SET_OVERLAY (WM_CAP_START + 51)
> >
> > #define HWND_MESSAGE ((HWND)-3)
> >
> > typedef struct videohdr_tag {
> > LPBYTE lpData;
> > DWORD dwBufferLength;
> > DWORD dwBytesUsed;
> > DWORD dwTimeCaptured;
> > DWORD dwUser;
> > DWORD dwFlags;
> > DWORD_PTR dwReserved[4];
> > } VIDEOHDR, NEAR *PVIDEOHDR, FAR * LPVIDEOHDR;
> > /* End of missing MinGW defines */
>
> Does cygwin have these?
>
> > struct vfw_ctx {
> > HWND hwnd;
> > int grabbed;
> > AVPacket *pkt;
> > };
> >
> > static int vfw_pixfmt( DWORD biCompression )
> > {
> > switch( biCompression ) {
> > case MKTAG( 'Y', 'U', 'Y', '2' ):
> > return PIX_FMT_YUYV422;
> > default:
> > return PIX_FMT_BGR24;
> > }
> > }
>
> See above.
>
> > static void dump_bih( AVFormatContext *s, BITMAPINFO *bih )
> > {
> > av_log( s, AV_LOG_DEBUG, " biSize:\t%d\n", (int) bih->bmiHeader.biSize );
> > av_log( s, AV_LOG_DEBUG, " biWidth:\t%d\n", (int) bih->bmiHeader.biWidth );
> > av_log( s, AV_LOG_DEBUG, " biHeight:\t%d\n", (int) bih->bmiHeader.biHeight );
> > av_log( s, AV_LOG_DEBUG, " biPlanes:\t%d\n", (int) bih->bmiHeader.biPlanes );
> > av_log( s, AV_LOG_DEBUG, " biBitCount:\t%d\n", (int) bih->bmiHeader.biBitCount );
> > av_log( s, AV_LOG_DEBUG, " biCompression:\t%d\t\"%.4s\"\n", (unsigned int)
> > bih->bmiHeader.biCompression, (char*) &bih->bmiHeader.biCompression );
> > av_log( s, AV_LOG_DEBUG, " biSizeImage:\t%d\n", (int) bih->bmiHeader.biSizeImage );
> > av_log( s, AV_LOG_DEBUG, " biXPelsPerMeter:\t%d\n", (int) bih->bmiHeader.biXPelsPerMeter );
> > av_log( s, AV_LOG_DEBUG, " biYPelsPerMeter:\t%d\n", (int) bih->bmiHeader.biYPelsPerMeter );
> > av_log( s, AV_LOG_DEBUG, " biClrUsed:\t%d\n", (int) bih->bmiHeader.biClrUsed );
> > av_log( s, AV_LOG_DEBUG, " biClrImportant:\t%d\n", (int) bih->bmiHeader.biClrImportant );
> > }
> >
> > static LRESULT __stdcall FrameCallbackProc( HWND hwnd, LPVIDEOHDR vdhdr )
> > {
> > struct vfw_ctx *ctx;
> > AVPacket *pkt;
> >
> > ctx = (struct vfw_ctx *) SendMessage( hwnd, WM_CAP_GET_USER_DATA, 0, 0 );
> > if( !ctx )
> > return FALSE;
> >
> > pkt = ctx->pkt;
> >
> > if( av_new_packet( pkt, vdhdr->dwBytesUsed ) < 0 )
> > return FALSE;
> >
> > pkt->pts = GetTickCount( );
> > memcpy( pkt->data, vdhdr->lpData, vdhdr->dwBytesUsed );
> >
> > ctx->grabbed = 1;
> >
> > return TRUE;
> > }
> >
> > static int vfw_read_header( AVFormatContext *s, AVFormatParameters *ap )
> > {
> > struct vfw_ctx *ctx = s->priv_data;
> > AVCodecContext *codec;
> > AVStream *st;
> > int devnum, ret;
> > BITMAPINFO *bih;
> >
> > if( s->flags & AVFMT_FLAG_NONBLOCK ) {
> > av_log( s, AV_LOG_ERROR, "Non blocking capture not yet implemented.\n" );
> > return AVERROR_IO;
> > }
> >
> > ctx->hwnd = capCreateCaptureWindow( NULL, 0, 0, 0, 0, 0, HWND_MESSAGE, 0 );
> > if( !ctx->hwnd ) {
> > av_log( s, AV_LOG_ERROR, "Could not create capture window.\n" );
> > return AVERROR_IO;
> > }
> >
> > /* If atoi fails, devnum==0 and the default device is used */
> > devnum = atoi( s->filename );
> >
> > ret = SendMessage( ctx->hwnd, WM_CAP_DRIVER_CONNECT, devnum, 0 );
> > if( !ret ) {
> > av_log( s, AV_LOG_ERROR, "Could not connect to device.\n" );
> > return AVERROR_IO;
> > }
>
> I'm not sure AVERROR_IO is the proper error code for those failures.
>
> > SendMessage( ctx->hwnd, WM_CAP_SET_OVERLAY, 0, 0 );
> > SendMessage( ctx->hwnd, WM_CAP_SET_PREVIEW, 0, 0 );
> >
> > ret = SendMessage( ctx->hwnd, WM_CAP_SET_CALLBACK_FRAME, 0,
> > (LPARAM) FrameCallbackProc );
> > if( !ret )
> > return AVERROR_IO;
> >
> > ret = SendMessage( ctx->hwnd, WM_CAP_SET_USER_DATA, 0, (LPARAM) ctx );
> > if( !ret )
> > return AVERROR_IO;
> >
> > st = av_new_stream( s, 0 );
> > if ( !st )
> > return AVERROR_NOMEM;
> >
> > ret = SendMessage( ctx->hwnd, WM_CAP_GET_VIDEOFORMAT, 0, 0 );
> > if( !ret )
> > return AVERROR_IO;
> > bih = av_malloc( ret );
> > if ( !bih )
> > return AVERROR_NOMEM;
> > ret = SendMessage( ctx->hwnd, WM_CAP_GET_VIDEOFORMAT, ret, (LPARAM) bih );
> > if( !ret )
> > return AVERROR_IO;
>
> Need to free bih in case of error here.
>
> > dump_bih( s, bih );
> >
> > codec = st->codec;
> > codec->time_base = ap->time_base;
> > codec->codec_type = CODEC_TYPE_VIDEO;
> > codec->width = bih->bmiHeader.biWidth;
> > codec->height = bih->bmiHeader.biHeight;
> > codec->codec_id = CODEC_ID_RAWVIDEO;
> > codec->pix_fmt = vfw_pixfmt( bih->bmiHeader.biCompression );
> >
> > av_set_pts_info( st, 32, 1, 1000 );
> >
> > av_free( bih );
> >
> > return 0;
> > }
> >
> > static int vfw_read_packet( AVFormatContext *s, AVPacket *pkt )
> > {
> > struct vfw_ctx *ctx = s->priv_data;
> > int ret;
> >
> > ctx->pkt = pkt;
> > ctx->grabbed = 0;
> >
> > ret = SendMessage( ctx->hwnd, WM_CAP_GRAB_FRAME, 0, 0 );
> > if( !ret || !ctx->grabbed )
> > return AVERROR_IO;
> >
> > return pkt->size;
> > }
> >
> > static int vfw_read_close( AVFormatContext *s )
> > {
> > struct vfw_ctx *ctx = s->priv_data;
> >
> > SendMessage( ctx->hwnd, WM_CAP_SET_CALLBACK_FRAME, 0, 0 );
> > SendMessage( ctx->hwnd, WM_CAP_DRIVER_DISCONNECT, 0, 0 );
> > DestroyWindow( ctx->hwnd );
> >
> > return 0;
> > }
> >
> > AVInputFormat vfwcap_demuxer = {
> > "vfwcap",
> > "VFW video capture",
> > sizeof(struct vfw_ctx),
> > NULL,
> > vfw_read_header,
> > vfw_read_packet,
> > vfw_read_close,
> > .flags = AVFMT_NOFILE,
> > };
> >
>
> --
> M?ns Rullg?rd
> mans at mansr.com
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at mplayerhq.hu
> https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel
>
--
Zuxy
Beauty is truth,
While truth is beauty.
PGP KeyID: E8555ED6
More information about the ffmpeg-devel
mailing list