static int decode_nal_units(H264Context *h, const uint8_t *buf, int buf_size,

                            int parse_extradata)

{

    MpegEncContext *const s     = &h->s;

    AVCodecContext *const avctx = s->avctx;

    H264Context *hx; ///< thread context

    int buf_index;

    int context_count;

    int next_avc;

    int pass = !(avctx->active_thread_type & FF_THREAD_FRAME);

    int nals_needed = 0; ///< number of NALs that need decoding before the next frame thread starts

    int nal_index;

    int idr_cleared=0;

    int first_slice = 0;



    h->nal_unit_type= 0;



    if(!s->slice_context_count)

         s->slice_context_count= 1;

    h->max_contexts = s->slice_context_count;

    if (!(s->flags2 & CODEC_FLAG2_CHUNKS)) {

        h->current_slice = 0;

        if (!s->first_field)

            s->current_picture_ptr = NULL;

        ff_h264_reset_sei(h);

    }



    if (h->nal_length_size == 4) {

        if (buf_size > 8 && AV_RB32(buf) == 1 && AV_RB32(buf+5) > (unsigned)buf_size) {

            h->is_avc = 0;

        }else if(buf_size > 3 && AV_RB32(buf) > 1 && AV_RB32(buf) <= (unsigned)buf_size)

            h->is_avc = 1;

    }



    for (; pass <= 1; pass++) {

        buf_index     = 0;

        context_count = 0;

        next_avc      = h->is_avc ? 0 : buf_size;

        nal_index     = 0;

        for (;;) {

            int consumed;

            int dst_length;

            int bit_length;

            const uint8_t *ptr;

            int i, nalsize = 0;

            int err;



            if (buf_index >= next_avc) {

                if (buf_index >= buf_size - h->nal_length_size)

                    break;

                nalsize = 0;

                for (i = 0; i < h->nal_length_size; i++)

                    nalsize = (nalsize << 8) | buf[buf_index++];

                if (nalsize <= 0 || nalsize > buf_size - buf_index) {

                    av_log(h->s.avctx, AV_LOG_ERROR,

                           "AVC: nal size %d\n", nalsize);

                    break;

                }

                next_avc = buf_index + nalsize;

            } else {

                // start code prefix search

                for (; buf_index + 3 < next_avc; buf_index++)

                    // This should always succeed in the first iteration.

                    if (buf[buf_index]     == 0 &&

                        buf[buf_index + 1] == 0 &&

                        buf[buf_index + 2] == 1)

                        break;



                if (buf_index + 3 >= buf_size) {

                    buf_index = buf_size;

                    break;

                }



                buf_index += 3;

                if (buf_index >= next_avc)

                    continue;

            }



            hx = h->thread_context[context_count];



            ptr = ff_h264_decode_nal(hx, buf + buf_index, &dst_length,

                                     &consumed, next_avc - buf_index);

            if (ptr == NULL || dst_length < 0) {

                buf_index = -1;

                goto end;

            }

            i = buf_index + consumed;

            if ((s->workaround_bugs & FF_BUG_AUTODETECT) && i + 3 < next_avc &&

                buf[i]     == 0x00 && buf[i + 1] == 0x00 &&

                buf[i + 2] == 0x01 && buf[i + 3] == 0xE0)

                s->workaround_bugs |= FF_BUG_TRUNCATED;



            if (!(s->workaround_bugs & FF_BUG_TRUNCATED))

                while(dst_length > 0 && ptr[dst_length - 1] == 0)

                    dst_length--;

            bit_length = !dst_length ? 0

                                     : (8 * dst_length -

                                        decode_rbsp_trailing(h, ptr + dst_length - 1));



            if (s->avctx->debug & FF_DEBUG_STARTCODE)

                av_log(h->s.avctx, AV_LOG_DEBUG, "NAL %d/%d at %d/%d length %d pass %d\n", hx->nal_unit_type, hx->nal_ref_idc, buf_index, buf_size, dst_length, pass);



            if (h->is_avc && (nalsize != consumed) && nalsize)

                av_log(h->s.avctx, AV_LOG_DEBUG,

                       "AVC: Consumed only %d bytes instead of %d\n",

                       consumed, nalsize);



            buf_index += consumed;

            nal_index++;



            if (pass == 0) {

                /* packets can sometimes contain multiple PPS/SPS,

                 * e.g. two PAFF field pictures in one packet, or a demuxer

                 * which splits NALs strangely if so, when frame threading we

                 * can't start the next thread until we've read all of them */

                switch (hx->nal_unit_type) {

                case NAL_SPS:

                case NAL_PPS:

                    nals_needed = nal_index;

                    break;

                case NAL_DPA:

                case NAL_IDR_SLICE:

                case NAL_SLICE:

                    init_get_bits(&hx->s.gb, ptr, bit_length);

                    if (!get_ue_golomb(&hx->s.gb) || !first_slice)

                        nals_needed = nal_index;

                    if (!first_slice)

                        first_slice = hx->nal_unit_type;

                }

                continue;

            }



            if (!first_slice)

                switch (hx->nal_unit_type) {

                case NAL_DPA:

                case NAL_IDR_SLICE:

                case NAL_SLICE:

                    first_slice = hx->nal_unit_type;

                }



            // FIXME do not discard SEI id

            if (avctx->skip_frame >= AVDISCARD_NONREF && h->nal_ref_idc == 0)

                continue;



again:

            /* Ignore every NAL unit type except PPS and SPS during extradata

             * parsing. Decoding slices is not possible in codec init

             * with frame-mt */

            if (parse_extradata && HAVE_THREADS &&

                (s->avctx->active_thread_type & FF_THREAD_FRAME) &&

                (hx->nal_unit_type != NAL_PPS &&

                 hx->nal_unit_type != NAL_SPS)) {

                av_log(avctx, AV_LOG_INFO, "Ignoring NAL unit %d during "

                       "extradata parsing\n", hx->nal_unit_type);

                hx->nal_unit_type = NAL_FF_IGNORE;

            }

            err = 0;



            if (h->decoding_extradata) {

                switch (hx->nal_unit_type) {

                case NAL_IDR_SLICE:

                case NAL_SLICE:

                case NAL_DPA:

                case NAL_DPB:

                case NAL_DPC:

                case NAL_AUXILIARY_SLICE:

                    av_log(h->s.avctx, AV_LOG_WARNING, "Ignoring NAL %d in global header\n", hx->nal_unit_type);

                    hx->nal_unit_type = NAL_FILLER_DATA;

                }

            }



            switch (hx->nal_unit_type) {

            case NAL_IDR_SLICE:

                if (first_slice != NAL_IDR_SLICE) {

                    av_log(h->s.avctx, AV_LOG_ERROR,

                           "Invalid mix of idr and non-idr slices\n");

                    buf_index = -1;

                    goto end;

                }

                if(!idr_cleared)

                    idr(h); // FIXME ensure we don't lose some frames if there is reordering

                idr_cleared = 1;

            case NAL_SLICE:

                init_get_bits(&hx->s.gb, ptr, bit_length);

                hx->intra_gb_ptr        =

                    hx->inter_gb_ptr    = &hx->s.gb;

                hx->s.data_partitioning = 0;



                if ((err = decode_slice_header(hx, h)))

                    break;



                if (h->sei_recovery_frame_cnt >= 0 && (h->frame_num != h->sei_recovery_frame_cnt || hx->slice_type_nos != AV_PICTURE_TYPE_I))

                    h->valid_recovery_point = 1;



                if (   h->sei_recovery_frame_cnt >= 0

                    && (   h->recovery_frame<0

                        || ((h->recovery_frame - h->frame_num) & ((1 << h->sps.log2_max_frame_num)-1)) > h->sei_recovery_frame_cnt)) {

                    h->recovery_frame = (h->frame_num + h->sei_recovery_frame_cnt) %

                                        (1 << h->sps.log2_max_frame_num);



                    if (!h->valid_recovery_point)

                        h->recovery_frame = h->frame_num;

                }



                s->current_picture_ptr->f.key_frame |=

                        (hx->nal_unit_type == NAL_IDR_SLICE);



                if (h->recovery_frame == h->frame_num) {

                    s->current_picture_ptr->sync |= 1;

                    h->recovery_frame = -1;

                }



                h->sync |= !!s->current_picture_ptr->f.key_frame;

                h->sync |= 3*!!(s->flags2 & CODEC_FLAG2_SHOW_ALL);

                s->current_picture_ptr->sync |= h->sync;



                if (h->current_slice == 1) {

                    if (!(s->flags2 & CODEC_FLAG2_CHUNKS))

                        decode_postinit(h, nal_index >= nals_needed);



                    if (s->avctx->hwaccel &&

                        s->avctx->hwaccel->start_frame(s->avctx, NULL, 0) < 0)

                        return -1;

                    if (CONFIG_H264_VDPAU_DECODER &&

                        s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU)

                        ff_vdpau_h264_picture_start(s);

                }



                if (hx->redundant_pic_count == 0 &&

                    (avctx->skip_frame < AVDISCARD_NONREF ||

                     hx->nal_ref_idc) &&

                    (avctx->skip_frame < AVDISCARD_BIDIR  ||

                     hx->slice_type_nos != AV_PICTURE_TYPE_B) &&

                    (avctx->skip_frame < AVDISCARD_NONKEY ||

                     hx->slice_type_nos == AV_PICTURE_TYPE_I) &&

                    avctx->skip_frame < AVDISCARD_ALL) {

                    if (avctx->hwaccel) {

                        if (avctx->hwaccel->decode_slice(avctx,

                                                         &buf[buf_index - consumed],

                                                         consumed) < 0)

                            return -1;

                    } else if (CONFIG_H264_VDPAU_DECODER &&

                               s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) {

                        static const uint8_t start_code[] = {

                            0x00, 0x00, 0x01 };

                        ff_vdpau_add_data_chunk(s, start_code,

                                                sizeof(start_code));

                        ff_vdpau_add_data_chunk(s, &buf[buf_index - consumed],

                                                consumed);

                    } else

                        context_count++;

                }

                break;

            case NAL_DPA:

                init_get_bits(&hx->s.gb, ptr, bit_length);

                hx->intra_gb_ptr =

                hx->inter_gb_ptr = NULL;



                if ((err = decode_slice_header(hx, h)) < 0)

                    break;



                hx->s.data_partitioning = 1;

                break;

            case NAL_DPB:

                init_get_bits(&hx->intra_gb, ptr, bit_length);

                hx->intra_gb_ptr = &hx->intra_gb;

                break;

            case NAL_DPC:

                init_get_bits(&hx->inter_gb, ptr, bit_length);

                hx->inter_gb_ptr = &hx->inter_gb;



                av_log(h->s.avctx, AV_LOG_ERROR, "Partitioned H.264 support is incomplete\n");

                break;



                if (hx->redundant_pic_count == 0 &&

                    hx->intra_gb_ptr &&

                    hx->s.data_partitioning &&

                    s->current_picture_ptr &&

                    s->context_initialized &&

                    (avctx->skip_frame < AVDISCARD_NONREF || hx->nal_ref_idc) &&

                    (avctx->skip_frame < AVDISCARD_BIDIR  ||

                     hx->slice_type_nos != AV_PICTURE_TYPE_B) &&

                    (avctx->skip_frame < AVDISCARD_NONKEY ||

                     hx->slice_type_nos == AV_PICTURE_TYPE_I) &&

                    avctx->skip_frame < AVDISCARD_ALL)

                    context_count++;

                break;

            case NAL_SEI:

                init_get_bits(&s->gb, ptr, bit_length);

                ff_h264_decode_sei(h);

                break;

            case NAL_SPS:

                init_get_bits(&s->gb, ptr, bit_length);

                if (ff_h264_decode_seq_parameter_set(h) < 0 && (h->is_avc ? (nalsize != consumed) && nalsize : 1)) {

                    av_log(h->s.avctx, AV_LOG_DEBUG,

                           "SPS decoding failure, trying again with the complete NAL\n");

                    if (h->is_avc)

                        av_assert0(next_avc - buf_index + consumed == nalsize);

                    if ((next_avc - buf_index + consumed - 1) >= INT_MAX/8)

                        break;

                    init_get_bits(&s->gb, &buf[buf_index + 1 - consumed],

                                  8*(next_avc - buf_index + consumed - 1));

                    ff_h264_decode_seq_parameter_set(h);

                }



                break;

            case NAL_PPS:

                init_get_bits(&s->gb, ptr, bit_length);

                ff_h264_decode_picture_parameter_set(h, bit_length);

                break;

            case NAL_AUD:

            case NAL_END_SEQUENCE:

            case NAL_END_STREAM:

            case NAL_FILLER_DATA:

            case NAL_SPS_EXT:

            case NAL_AUXILIARY_SLICE:

                break;

            case NAL_FF_IGNORE:

                break;

            default:

                av_log(avctx, AV_LOG_DEBUG, "Unknown NAL code: %d (%d bits)\n",

                       hx->nal_unit_type, bit_length);

            }



            if (context_count == h->max_contexts) {

                execute_decode_slices(h, context_count);

                context_count = 0;

            }



            if (err < 0)

                av_log(h->s.avctx, AV_LOG_ERROR, "decode_slice_header error\n");

            else if (err == 1) {

                /* Slice could not be decoded in parallel mode, copy down

                 * NAL unit stuff to context 0 and restart. Note that

                 * rbsp_buffer is not transferred, but since we no longer

                 * run in parallel mode this should not be an issue. */

                h->nal_unit_type = hx->nal_unit_type;

                h->nal_ref_idc   = hx->nal_ref_idc;

                hx               = h;

                goto again;

            }

        }

    }

    if (context_count)

        execute_decode_slices(h, context_count);



end:

    /* clean up */

    if (s->current_picture_ptr && s->current_picture_ptr->owner2 == s &&

        !s->droppable) {

        ff_thread_report_progress(&s->current_picture_ptr->f, INT_MAX,

                                  s->picture_structure == PICT_BOTTOM_FIELD);

    }



    return buf_index;

}
