video.c

/*****************************************************************************
 * video.c: video decoder using the libavcodec library
 *****************************************************************************
 * Copyright (C) 1999-2001 VLC authors and VideoLAN
 * $Id$
 *
 * Authors: Laurent Aimar <fenrir@via.ecp.fr>
 *          Gildas Bazin <gbazin@videolan.org>
 *
 * This program 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.
 *
 * This program 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 this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <vlc_common.h>
#include <vlc_codec.h>
#include <vlc_avcodec.h>
#include <vlc_cpu.h>
#include <assert.h>

#include <libavcodec/avcodec.h>
#include <libavutil/mem.h>
#include <libavutil/pixdesc.h>

#include "avcodec.h"
#include "va.h"

/*****************************************************************************
 * decoder_sys_t : decoder descriptor
 *****************************************************************************/
struct decoder_sys_t
{
    AVCODEC_COMMON_MEMBERS

    /* Video decoder specific part */
    mtime_t i_pts;

    AVFrame          *p_ff_pic;

    /* for frame skipping algo */
    bool b_hurry_up;
    enum AVDiscard i_skip_frame;
    enum AVDiscard i_skip_idct;

    /* how many decoded frames are late */
    int     i_late_frames;
    mtime_t i_late_frames_start;

    /* for direct rendering */
    bool b_direct_rendering;
    int  i_direct_rendering_used;

    bool b_has_b_frames;

    /* Hack to force display of still pictures */
    bool b_first_frame;


    /* */
    bool palette_sent;

    /* */
    bool b_flush;

    /* VA API */
    vlc_va_t *p_va;

    vlc_sem_t sem_mt;
};

#ifdef HAVE_AVCODEC_MT
#   define wait_mt(s) vlc_sem_wait( &s->sem_mt )
#   define post_mt(s) vlc_sem_post( &s->sem_mt )
#else
#   define wait_mt(s)
#   define post_mt(s)
#endif

/*****************************************************************************
 * Local prototypes
 *****************************************************************************/
static void ffmpeg_InitCodec      ( decoder_t * );
static void ffmpeg_CopyPicture    ( decoder_t *, picture_t *, AVFrame * );
#if LIBAVCODEC_VERSION_MAJOR >= 55
static int lavc_GetFrame(struct AVCodecContext *, AVFrame *, int);
#else
static int  ffmpeg_GetFrameBuf    ( struct AVCodecContext *, AVFrame * );
static void ffmpeg_ReleaseFrameBuf( struct AVCodecContext *, AVFrame * );
#endif
static enum PixelFormat ffmpeg_GetFormat( AVCodecContext *,
                                          const enum PixelFormat * );
static picture_t *DecodeVideo( decoder_t *, block_t ** );

static uint32_t ffmpeg_CodecTag( vlc_fourcc_t fcc )
{
    uint8_t *p = (uint8_t*)&fcc;
    return p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24);
}

/*****************************************************************************
 * Local Functions
 *****************************************************************************/

/* Returns a new picture buffer */
static inline picture_t *ffmpeg_NewPictBuf( decoder_t *p_dec,
                                            AVCodecContext *p_context )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    int width = p_context->coded_width;
    int height = p_context->coded_height;

    if( p_sys->p_va == NULL )
    {
        int aligns[AV_NUM_DATA_POINTERS];

        avcodec_align_dimensions2(p_context, &width, &height, aligns);
    }


    if( width == 0 || height == 0 || width > 8192 || height > 8192 )
    {
        msg_Err( p_dec, "Invalid frame size %dx%d.", width, height );
        return NULL; /* invalid display size */
    }
    p_dec->fmt_out.video.i_width = width;
    p_dec->fmt_out.video.i_height = height;

    if( width != p_context->width || height != p_context->height )
    {
        p_dec->fmt_out.video.i_visible_width = p_context->width;
        p_dec->fmt_out.video.i_visible_height = p_context->height;
    }
    else
    {
        p_dec->fmt_out.video.i_visible_width = width;
        p_dec->fmt_out.video.i_visible_height = height;
    }

    if( !p_sys->p_va && GetVlcChroma( &p_dec->fmt_out.video, p_context->pix_fmt ) )
    {
        /* we are doomed, but not really, because most codecs set their pix_fmt
         * much later
         * FIXME does it make sense here ? */
        p_dec->fmt_out.video.i_chroma = VLC_CODEC_I420;
    }
    p_dec->fmt_out.i_codec = p_dec->fmt_out.video.i_chroma;

    /* If an aspect-ratio was specified in the input format then force it */
    if( p_dec->fmt_in.video.i_sar_num > 0 && p_dec->fmt_in.video.i_sar_den > 0 )
    {
        p_dec->fmt_out.video.i_sar_num = p_dec->fmt_in.video.i_sar_num;
        p_dec->fmt_out.video.i_sar_den = p_dec->fmt_in.video.i_sar_den;
    }
    else
    {
        p_dec->fmt_out.video.i_sar_num = p_context->sample_aspect_ratio.num;
        p_dec->fmt_out.video.i_sar_den = p_context->sample_aspect_ratio.den;

        if( !p_dec->fmt_out.video.i_sar_num || !p_dec->fmt_out.video.i_sar_den )
        {
            p_dec->fmt_out.video.i_sar_num = 1;
            p_dec->fmt_out.video.i_sar_den = 1;
        }
    }

    if( p_dec->fmt_in.video.i_frame_rate > 0 &&
        p_dec->fmt_in.video.i_frame_rate_base > 0 )
    {
        p_dec->fmt_out.video.i_frame_rate =
            p_dec->fmt_in.video.i_frame_rate;
        p_dec->fmt_out.video.i_frame_rate_base =
            p_dec->fmt_in.video.i_frame_rate_base;
    }
    else if( p_context->time_base.num > 0 && p_context->time_base.den > 0 )
    {
        p_dec->fmt_out.video.i_frame_rate = p_context->time_base.den;
        p_dec->fmt_out.video.i_frame_rate_base = p_context->time_base.num * __MAX( p_context->ticks_per_frame, 1 );
    }

    return decoder_NewPicture( p_dec );
}

static int OpenVideoCodec( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;

    if( p_sys->p_context->extradata_size <= 0 )
    {
        if( p_sys->i_codec_id == AV_CODEC_ID_VC1 ||
            p_sys->i_codec_id == AV_CODEC_ID_THEORA )
        {
            msg_Warn( p_dec, "waiting for extra data for codec %s",
                      p_sys->psz_namecodec );
            return 1;
        }
    }

    p_sys->p_context->width  = p_dec->fmt_in.video.i_visible_width;
    p_sys->p_context->height = p_dec->fmt_in.video.i_visible_height;
    if (p_sys->p_context->width  == 0)
        p_sys->p_context->width  = p_dec->fmt_in.video.i_width;
    else if (p_sys->p_context->width != p_dec->fmt_in.video.i_width)
        p_sys->p_context->coded_width = p_dec->fmt_in.video.i_width;
    if (p_sys->p_context->height == 0)
        p_sys->p_context->height = p_dec->fmt_in.video.i_height;
    else if (p_sys->p_context->height != p_dec->fmt_in.video.i_height)
        p_sys->p_context->coded_height = p_dec->fmt_in.video.i_height;
    p_sys->p_context->bits_per_coded_sample = p_dec->fmt_in.video.i_bits_per_pixel;

    int ret = ffmpeg_OpenCodec( p_dec );
    if( ret < 0 )
        return ret;

#ifdef HAVE_AVCODEC_MT
    switch( p_sys->p_context->active_thread_type )
    {
        case FF_THREAD_FRAME:
            msg_Dbg( p_dec, "using frame thread mode with %d threads",
                     p_sys->p_context->thread_count );
            break;
        case FF_THREAD_SLICE:
            msg_Dbg( p_dec, "using slice thread mode with %d threads",
                     p_sys->p_context->thread_count );
            break;
        case 0:
            if( p_sys->p_context->thread_count > 1 )
                msg_Warn( p_dec, "failed to enable threaded decoding" );
            break;
        default:
            msg_Warn( p_dec, "using unknown thread mode with %d threads",
                      p_sys->p_context->thread_count );
            break;
    }
#endif
    return VLC_SUCCESS;
}

/*****************************************************************************
 * InitVideo: initialize the video decoder
 *****************************************************************************
 * the ffmpeg codec will be opened, some memory allocated. The vout is not yet
 * opened (done after the first decoded frame).
 *****************************************************************************/
int InitVideoDec( decoder_t *p_dec, AVCodecContext *p_context,
                  AVCodec *p_codec, int i_codec_id, const char *psz_namecodec )
{
    decoder_sys_t *p_sys;
    int i_val;

    /* Allocate the memory needed to store the decoder's structure */
    if( ( p_dec->p_sys = p_sys = calloc( 1, sizeof(decoder_sys_t) ) ) == NULL )
        return VLC_ENOMEM;

    p_codec->type = AVMEDIA_TYPE_VIDEO;
    p_context->codec_type = AVMEDIA_TYPE_VIDEO;
    p_context->codec_id = i_codec_id;
    p_sys->p_context = p_context;
    p_sys->p_codec = p_codec;
    p_sys->i_codec_id = i_codec_id;
    p_sys->psz_namecodec = psz_namecodec;
    p_sys->p_ff_pic = avcodec_alloc_frame();
    p_sys->b_delayed_open = true;
    p_sys->p_va = NULL;
    vlc_sem_init( &p_sys->sem_mt, 0 );

    /* ***** Fill p_context with init values ***** */
    p_context->codec_tag = ffmpeg_CodecTag( p_dec->fmt_in.i_original_fourcc ?: p_dec->fmt_in.i_codec );

    /*  ***** Get configuration of ffmpeg plugin ***** */
    p_context->workaround_bugs =
        var_InheritInteger( p_dec, "avcodec-workaround-bugs" );
    p_context->err_recognition =
        var_InheritInteger( p_dec, "avcodec-error-resilience" );

    if( var_CreateGetBool( p_dec, "grayscale" ) )
        p_context->flags |= CODEC_FLAG_GRAY;

    /* ***** Output always the frames ***** */
#if LIBAVCODEC_VERSION_CHECK(55, 23, 1, 40, 101)
    p_context->flags |= CODEC_FLAG_OUTPUT_CORRUPT;
#endif

    i_val = var_CreateGetInteger( p_dec, "avcodec-vismv" );
    if( i_val )
        p_context->debug_mv = i_val;

    i_val = var_CreateGetInteger( p_dec, "avcodec-skiploopfilter" );
    if( i_val >= 4 ) p_context->skip_loop_filter = AVDISCARD_ALL;
    else if( i_val == 3 ) p_context->skip_loop_filter = AVDISCARD_NONKEY;
    else if( i_val == 2 ) p_context->skip_loop_filter = AVDISCARD_BIDIR;
    else if( i_val == 1 ) p_context->skip_loop_filter = AVDISCARD_NONREF;

    if( var_CreateGetBool( p_dec, "avcodec-fast" ) )
        p_context->flags2 |= CODEC_FLAG2_FAST;

    /* ***** libavcodec frame skipping ***** */
    p_sys->b_hurry_up = var_CreateGetBool( p_dec, "avcodec-hurry-up" );

    i_val = var_CreateGetInteger( p_dec, "avcodec-skip-frame" );
    if( i_val >= 4 ) p_context->skip_frame = AVDISCARD_ALL;
    else if( i_val == 3 ) p_context->skip_frame = AVDISCARD_NONKEY;
    else if( i_val == 2 ) p_context->skip_frame = AVDISCARD_BIDIR;
    else if( i_val == 1 ) p_context->skip_frame = AVDISCARD_NONREF;
    else if( i_val == -1 ) p_context->skip_frame = AVDISCARD_NONE;
    else p_context->skip_frame = AVDISCARD_DEFAULT;
    p_sys->i_skip_frame = p_context->skip_frame;

    i_val = var_CreateGetInteger( p_dec, "avcodec-skip-idct" );
    if( i_val >= 4 ) p_context->skip_idct = AVDISCARD_ALL;
    else if( i_val == 3 ) p_context->skip_idct = AVDISCARD_NONKEY;
    else if( i_val == 2 ) p_context->skip_idct = AVDISCARD_BIDIR;
    else if( i_val == 1 ) p_context->skip_idct = AVDISCARD_NONREF;
    else if( i_val == -1 ) p_context->skip_idct = AVDISCARD_NONE;
    else p_context->skip_idct = AVDISCARD_DEFAULT;
    p_sys->i_skip_idct = p_context->skip_idct;

    /* ***** libavcodec direct rendering ***** */
    p_sys->b_direct_rendering = false;
    p_sys->i_direct_rendering_used = -1;
    if( var_CreateGetBool( p_dec, "avcodec-dr" ) &&
       (p_sys->p_codec->capabilities & CODEC_CAP_DR1) &&
        /* No idea why ... but this fixes flickering on some TSCC streams */
        p_sys->i_codec_id != AV_CODEC_ID_TSCC && p_sys->i_codec_id != AV_CODEC_ID_CSCD &&
        p_sys->i_codec_id != AV_CODEC_ID_CINEPAK &&
        !p_context->debug_mv )
    {
        /* Some codecs set pix_fmt only after the 1st frame has been decoded,
         * so we need to do another check in ffmpeg_GetFrameBuf() */
        p_sys->b_direct_rendering = true;
    }

    /* libavcodec doesn't properly release old pictures when frames are skipped */
    //if( p_sys->b_hurry_up ) p_sys->b_direct_rendering = false;
    if( p_sys->b_direct_rendering )
    {
        msg_Dbg( p_dec, "trying to use direct rendering" );
        p_context->flags |= CODEC_FLAG_EMU_EDGE;
    }
    else
    {
        msg_Dbg( p_dec, "direct rendering is disabled" );
    }

    p_context->get_format = ffmpeg_GetFormat;
    /* Always use our get_buffer wrapper so we can calculate the
     * PTS correctly */
#if LIBAVCODEC_VERSION_MAJOR >= 55
    p_context->get_buffer2 = lavc_GetFrame;
#else
    p_context->get_buffer = ffmpeg_GetFrameBuf;
    p_context->reget_buffer = avcodec_default_reget_buffer;
    p_context->release_buffer = ffmpeg_ReleaseFrameBuf;
#endif
    p_context->opaque = p_dec;

#ifdef HAVE_AVCODEC_MT
    int i_thread_count = var_InheritInteger( p_dec, "avcodec-threads" );
    if( i_thread_count <= 0 )
    {
        i_thread_count = vlc_GetCPUCount();
        if( i_thread_count > 1 )
            i_thread_count++;

        //FIXME: take in count the decoding time
        i_thread_count = __MIN( i_thread_count, 4 );
    }
    i_thread_count = __MIN( i_thread_count, 16 );
    msg_Dbg( p_dec, "allowing %d thread(s) for decoding", i_thread_count );
    p_context->thread_count = i_thread_count;
    p_context->thread_safe_callbacks = true;

    switch( i_codec_id )
    {
        case AV_CODEC_ID_MPEG4:
        case AV_CODEC_ID_H263:
            p_context->thread_type = 0;
            break;
        case AV_CODEC_ID_MPEG1VIDEO:
        case AV_CODEC_ID_MPEG2VIDEO:
            p_context->thread_type &= ~FF_THREAD_SLICE;
            /* fall through */
# if (LIBAVCODEC_VERSION_INT < AV_VERSION_INT(55, 1, 0))
        case AV_CODEC_ID_H264:
        case AV_CODEC_ID_VC1:
        case AV_CODEC_ID_WMV3:
            p_context->thread_type &= ~FF_THREAD_FRAME;
# endif
    }

    /* Workaround: frame multithreading is not compatible with
     * DXVA2. When a frame is being copied to host memory, the frame
     * is locked and cannot be used as a reference frame
     * simultaneously and thus decoding fails for some frames. This
     * causes major image corruption. */
# if defined(_WIN32)
    char *avcodec_hw = var_InheritString( p_dec, "avcodec-hw" );
    if( avcodec_hw == NULL || strcasecmp( avcodec_hw, "none" ) )
    {
        msg_Warn( p_dec, "threaded frame decoding is not compatible with DXVA2, disabled" );
        p_context->thread_type &= ~FF_THREAD_FRAME;
    }
    free( avcodec_hw );
# endif

    if( p_context->thread_type & FF_THREAD_FRAME )
        p_dec->i_extra_picture_buffers = 2 * p_context->thread_count;
#endif

    /* ***** misc init ***** */
    p_sys->i_pts = VLC_TS_INVALID;
    p_sys->b_has_b_frames = false;
    p_sys->b_first_frame = true;
    p_sys->b_flush = false;
    p_sys->i_late_frames = 0;

    /* Set output properties */
    p_dec->fmt_out.i_cat = VIDEO_ES;
    if( GetVlcChroma( &p_dec->fmt_out.video, p_context->pix_fmt ) != VLC_SUCCESS )
    {
        /* we are doomed. but not really, because most codecs set their pix_fmt later on */
        p_dec->fmt_out.i_codec = VLC_CODEC_I420;
    }
    p_dec->fmt_out.i_codec = p_dec->fmt_out.video.i_chroma;

    p_dec->fmt_out.video.orientation = p_dec->fmt_in.video.orientation;

    if( p_dec->fmt_in.video.p_palette ) {
        p_sys->palette_sent = false;
        p_dec->fmt_out.video.p_palette = malloc( sizeof(video_palette_t) );
        if( p_dec->fmt_out.video.p_palette )
            *p_dec->fmt_out.video.p_palette = *p_dec->fmt_in.video.p_palette;
    } else
        p_sys->palette_sent = true;

    /* ***** init this codec with special data ***** */
    ffmpeg_InitCodec( p_dec );

    /* ***** Open the codec ***** */
    if( OpenVideoCodec( p_dec ) < 0 )
    {
        avcodec_free_frame( &p_sys->p_ff_pic );
        vlc_sem_destroy( &p_sys->sem_mt );
        free( p_sys );
        return VLC_EGENERIC;
    }

    p_dec->pf_decode_video = DecodeVideo;
    return VLC_SUCCESS;
}

/*****************************************************************************
 * DecodeVideo: Called to decode one or more frames
 *****************************************************************************/
static picture_t *DecodeVideo( decoder_t *p_dec, block_t **pp_block )
{
    decoder_sys_t *p_sys = p_dec->p_sys;
    AVCodecContext *p_context = p_sys->p_context;
    int b_drawpicture;
    block_t *p_block;

    if( !pp_block )
        return NULL;

    if( !p_context->extradata_size && p_dec->fmt_in.i_extra )
    {
        ffmpeg_InitCodec( p_dec );
        if( p_sys->b_delayed_open )
            OpenVideoCodec( p_dec );
    }

    p_block = *pp_block;
    if(!p_block && !(p_sys->p_codec->capabilities & CODEC_CAP_DELAY) )
        return NULL;

    if( p_sys->b_delayed_open )
    {
        if( p_block )
            block_Release( p_block );
        return NULL;
    }

    if( p_block)
    {
        if( p_block->i_flags & (BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
        {
            p_sys->i_pts = VLC_TS_INVALID; /* To make sure we recover properly */

            p_sys->i_late_frames = 0;

            post_mt( p_sys );
            if( p_block->i_flags & BLOCK_FLAG_DISCONTINUITY )
                avcodec_flush_buffers( p_context );
            wait_mt( p_sys );

            block_Release( p_block );
            return NULL;
        }

        if( p_block->i_flags & BLOCK_FLAG_PREROLL )
        {
            /* Do not care about late frames when prerolling
             * TODO avoid decoding of non reference frame
             * (ie all B except for H264 where it depends only on nal_ref_idc) */
            p_sys->i_late_frames = 0;
        }
    }

    if( !p_dec->b_pace_control && (p_sys->i_late_frames > 0) &&
        (mdate() - p_sys->i_late_frames_start > INT64_C(5000000)) )
    {
        if( p_sys->i_pts > VLC_TS_INVALID )
        {
            p_sys->i_pts = VLC_TS_INVALID; /* To make sure we recover properly */
        }
        if( p_block )
            block_Release( p_block );
        p_sys->i_late_frames--;
        msg_Err( p_dec, "more than 5 seconds of late video -> "
                 "dropping frame (computer too slow ?)" );
        return NULL;
    }

    /* A good idea could be to decode all I pictures and see for the other */
    if( !p_dec->b_pace_control &&
        p_sys->b_hurry_up &&
        (p_sys->i_late_frames > 4) )
    {
        b_drawpicture = 0;
        if( p_sys->i_late_frames < 12 )
        {
            p_context->skip_frame =
                    (p_sys->i_skip_frame <= AVDISCARD_NONREF) ?
                    AVDISCARD_NONREF : p_sys->i_skip_frame;
        }
        else
        {
            /* picture too late, won't decode
             * but break picture until a new I, and for mpeg4 ...*/
            p_sys->i_late_frames--; /* needed else it will never be decrease */
            if( p_block )
                block_Release( p_block );
            msg_Warn( p_dec, "More than 4 late frames, dropping frame" );
            return NULL;
        }
    }
    else
    {
        if( p_sys->b_hurry_up )
            p_context->skip_frame = p_sys->i_skip_frame;
        if( !p_block || !(p_block->i_flags & BLOCK_FLAG_PREROLL) )
            b_drawpicture = 1;
        else
            b_drawpicture = 0;
    }

    if( p_context->width <= 0 || p_context->height <= 0 )
    {
        if( p_sys->b_hurry_up )
            p_context->skip_frame = p_sys->i_skip_frame;
    }
    else if( !b_drawpicture )
    {
        /* It creates broken picture
         * FIXME either our parser or ffmpeg is broken */
#if 0
        if( p_sys->b_hurry_up )
            p_context->skip_frame = __MAX( p_context->skip_frame,
                                                  AVDISCARD_NONREF );
#endif
    }

    /*
     * Do the actual decoding now */

    /* Don't forget that libavcodec requires a little more bytes
     * that the real frame size */
    if( p_block && p_block->i_buffer > 0 )
    {
        p_sys->b_flush = ( p_block->i_flags & BLOCK_FLAG_END_OF_SEQUENCE ) != 0;

        p_block = block_Realloc( p_block, 0,
                            p_block->i_buffer + FF_INPUT_BUFFER_PADDING_SIZE );
        if( !p_block )
            return NULL;
        p_block->i_buffer -= FF_INPUT_BUFFER_PADDING_SIZE;
        *pp_block = p_block;
        memset( p_block->p_buffer + p_block->i_buffer, 0,
                FF_INPUT_BUFFER_PADDING_SIZE );
    }

    while( !p_block || p_block->i_buffer > 0 || p_sys->b_flush )
    {
        int i_used, b_gotpicture;
        picture_t *p_pic;
        AVPacket pkt;

        post_mt( p_sys );

        av_init_packet( &pkt );
        if( p_block )
        {
            pkt.data = p_block->p_buffer;
            pkt.size = p_block->i_buffer;
            pkt.pts = p_block->i_pts;
            pkt.dts = p_block->i_dts;
        }
        else
        {
            /* Return delayed frames if codec has CODEC_CAP_DELAY */
            pkt.data = NULL;
            pkt.size = 0;
        }

        if( !p_sys->palette_sent )
        {
            uint8_t *pal = av_packet_new_side_data(&pkt, AV_PKT_DATA_PALETTE, AVPALETTE_SIZE);
            if (pal) {
                memcpy(pal, p_dec->fmt_in.video.p_palette->palette, AVPALETTE_SIZE);
                p_sys->palette_sent = true;
            }
        }

        /* Make sure we don't reuse the same timestamps twice */
        if( p_block )
        {
            p_block->i_pts =
            p_block->i_dts = VLC_TS_INVALID;
        }

        i_used = avcodec_decode_video2( p_context, p_sys->p_ff_pic,
                                       &b_gotpicture, &pkt );
        av_free_packet( &pkt );

        wait_mt( p_sys );

        if( p_sys->b_flush )
            p_sys->b_first_frame = true;

        if( p_block )
        {
            if( p_block->i_buffer <= 0 )
                p_sys->b_flush = false;

            if( i_used < 0 )
            {
                if( b_drawpicture )
                    msg_Warn( p_dec, "cannot decode one frame (%zu bytes)",
                            p_block->i_buffer );
                block_Release( p_block );
                return NULL;
            }
            else if( (unsigned)i_used > p_block->i_buffer ||
                    p_context->thread_count > 1 )
            {
                i_used = p_block->i_buffer;
            }

            /* Consumed bytes */
            p_block->i_buffer -= i_used;
            p_block->p_buffer += i_used;
        }

        /* Nothing to display */
        if( !b_gotpicture )
        {
            if( i_used == 0 ) break;
            continue;
        }

        /* Sanity check (seems to be needed for some streams) */
        if( p_sys->p_ff_pic->pict_type == AV_PICTURE_TYPE_B)
        {
            p_sys->b_has_b_frames = true;
        }

        /* Compute the PTS */
        mtime_t i_pts =
                    p_sys->p_ff_pic->pkt_pts;
        if (i_pts <= VLC_TS_INVALID)
            i_pts = p_sys->p_ff_pic->pkt_dts;

        if( i_pts <= VLC_TS_INVALID )
            i_pts = p_sys->i_pts;

        /* Interpolate the next PTS */
        if( i_pts > VLC_TS_INVALID )
            p_sys->i_pts = i_pts;
        if( p_sys->i_pts > VLC_TS_INVALID )
        {
            /* interpolate the next PTS */
            if( p_dec->fmt_in.video.i_frame_rate > 0 &&
                p_dec->fmt_in.video.i_frame_rate_base > 0 )
            {
                p_sys->i_pts += CLOCK_FREQ *
                    (2 + p_sys->p_ff_pic->repeat_pict) *
                    p_dec->fmt_in.video.i_frame_rate_base /
                    (2 * p_dec->fmt_in.video.i_frame_rate);
            }
            else if( p_context->time_base.den > 0 )
            {
                int i_tick = p_context->ticks_per_frame;
                if( i_tick <= 0 )
                    i_tick = 1;

                p_sys->i_pts += CLOCK_FREQ *
                    (2 + p_sys->p_ff_pic->repeat_pict) *
                    i_tick * p_context->time_base.num /
                    (2 * p_context->time_base.den);
            }
        }

        /* Update frame late count (except when doing preroll) */
        mtime_t i_display_date = 0;
        if( !p_block || !(p_block->i_flags & BLOCK_FLAG_PREROLL) )
            i_display_date = decoder_GetDisplayDate( p_dec, i_pts );

        if( i_display_date > 0 && i_display_date <= mdate() )
        {
            p_sys->i_late_frames++;
            if( p_sys->i_late_frames == 1 )
                p_sys->i_late_frames_start = mdate();
        }
        else
        {
            p_sys->i_late_frames = 0;
        }

        if( !b_drawpicture || ( !p_sys->p_va && !p_sys->p_ff_pic->linesize[0] ) )
            continue;

        if( p_sys->p_va != NULL || p_sys->p_ff_pic->opaque == NULL )
        {
            /* Get a new picture */
            p_pic = ffmpeg_NewPictBuf( p_dec, p_context );
            if( !p_pic )
            {
                if( p_block )
                    block_Release( p_block );
                return NULL;
            }

            /* Fill p_picture_t from AVVideoFrame and do chroma conversion
             * if needed */
            ffmpeg_CopyPicture( p_dec, p_pic, p_sys->p_ff_pic );
        }
        else
        {
            p_pic = (picture_t *)p_sys->p_ff_pic->opaque;
            decoder_LinkPicture( p_dec, p_pic );
        }

        if( !p_dec->fmt_in.video.i_sar_num || !p_dec->fmt_in.video.i_sar_den )
        {
            /* Fetch again the aspect ratio in case it changed */
            p_dec->fmt_out.video.i_sar_num
                = p_context->sample_aspect_ratio.num;
            p_dec->fmt_out.video.i_sar_den
                = p_context->sample_aspect_ratio.den;

            if( !p_dec->fmt_out.video.i_sar_num || !p_dec->fmt_out.video.i_sar_den )
            {
                p_dec->fmt_out.video.i_sar_num = 1;
                p_dec->fmt_out.video.i_sar_den = 1;
            }
        }

        /* Send decoded frame to vout */
        if( i_pts > VLC_TS_INVALID)
        {
            p_pic->date = i_pts;

            if( p_sys->b_first_frame )
            {
                /* Hack to force display of still pictures */
                p_sys->b_first_frame = false;
                p_pic->b_force = true;
            }

            p_pic->i_nb_fields = 2 + p_sys->p_ff_pic->repeat_pict;
            p_pic->b_progressive = !p_sys->p_ff_pic->interlaced_frame;
            p_pic->b_top_field_first = p_sys->p_ff_pic->top_field_first;

            return p_pic;
        }
        else
        {
            decoder_DeletePicture( p_dec, p_pic );
        }
    }

    if( p_block )
        block_Release( p_block );
    return NULL;
}

/*****************************************************************************
 * EndVideo: decoder destruction
 *****************************************************************************
 * This function is called when the thread ends after a successful
 * initialization.
 *****************************************************************************/
void EndVideoDec( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;

    post_mt( p_sys );

    /* do not flush buffers if codec hasn't been opened (theora/vorbis/VC1) */
    if( p_sys->p_context->codec )
        avcodec_flush_buffers( p_sys->p_context );

    wait_mt( p_sys );

    if( p_sys->p_ff_pic )
        avcodec_free_frame( &p_sys->p_ff_pic );

    if( p_sys->p_va )
        vlc_va_Delete( p_sys->p_va );

    vlc_sem_destroy( &p_sys->sem_mt );
}

/*****************************************************************************
 * ffmpeg_InitCodec: setup codec extra initialization data for ffmpeg
 *****************************************************************************/
static void ffmpeg_InitCodec( decoder_t *p_dec )
{
    decoder_sys_t *p_sys = p_dec->p_sys;