From f0194e860e33cb60a80305eae2262b2e7977c908 Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Tue, 4 Jan 2022 06:05:59 +0100 Subject: avcodec/mpeg4video: Skip unneeded element when parsing picture header Namely, skip some elements that are only useful for a decoder when calling ff_mpeg4_decode_picture_header() from the MPEG-4 parser. In particular, this ensures that the VLCs need no longer be initialized by the parser. Signed-off-by: Andreas Rheinhardt --- libavcodec/h263dec.c | 4 ++-- libavcodec/mpeg4video.h | 3 ++- libavcodec/mpeg4video_parser.c | 4 ++-- libavcodec/mpeg4videodec.c | 18 +++++++++++++++--- 4 files changed, 21 insertions(+), 8 deletions(-) diff --git a/libavcodec/h263dec.c b/libavcodec/h263dec.c index 2682a7f43a..11e80cb9e9 100644 --- a/libavcodec/h263dec.c +++ b/libavcodec/h263dec.c @@ -507,9 +507,9 @@ retry: GetBitContext gb; if (init_get_bits8(&gb, s->avctx->extradata, s->avctx->extradata_size) >= 0 ) - ff_mpeg4_decode_picture_header(avctx->priv_data, &gb, 1); + ff_mpeg4_decode_picture_header(avctx->priv_data, &gb, 1, 0); } - ret = ff_mpeg4_decode_picture_header(avctx->priv_data, &s->gb, 0); + ret = ff_mpeg4_decode_picture_header(avctx->priv_data, &s->gb, 0, 0); } else if (CONFIG_H263I_DECODER && s->codec_id == AV_CODEC_ID_H263I) { ret = ff_intel_h263_decode_picture_header(s); } else if (CONFIG_FLV_DECODER && s->h263_flv) { diff --git a/libavcodec/mpeg4video.h b/libavcodec/mpeg4video.h index 3db6f85153..ee8eea7121 100644 --- a/libavcodec/mpeg4video.h +++ b/libavcodec/mpeg4video.h @@ -160,7 +160,8 @@ void ff_mpeg4_pred_ac(MpegEncContext *s, int16_t *block, int n, void ff_set_mpeg4_time(MpegEncContext *s); int ff_mpeg4_encode_picture_header(MpegEncContext *s, int picture_number); -int ff_mpeg4_decode_picture_header(Mpeg4DecContext *ctx, GetBitContext *gb, int header); +int ff_mpeg4_decode_picture_header(Mpeg4DecContext *ctx, GetBitContext *gb, + int header, int parse_only); void ff_mpeg4_encode_video_packet_header(MpegEncContext *s); void ff_mpeg4_clean_buffers(MpegEncContext *s); void ff_mpeg4_stuffing(PutBitContext *pbc); diff --git a/libavcodec/mpeg4video_parser.c b/libavcodec/mpeg4video_parser.c index c68c966259..9e96619a12 100644 --- a/libavcodec/mpeg4video_parser.c +++ b/libavcodec/mpeg4video_parser.c @@ -100,13 +100,13 @@ static int mpeg4_decode_header(AVCodecParserContext *s1, AVCodecContext *avctx, if (avctx->extradata_size && pc->first_picture) { init_get_bits(gb, avctx->extradata, avctx->extradata_size * 8); - ret = ff_mpeg4_decode_picture_header(dec_ctx, gb, 1); + ret = ff_mpeg4_decode_picture_header(dec_ctx, gb, 1, 1); if (ret < 0) av_log(avctx, AV_LOG_WARNING, "Failed to parse extradata\n"); } init_get_bits(gb, buf, 8 * buf_size); - ret = ff_mpeg4_decode_picture_header(dec_ctx, gb, 0); + ret = ff_mpeg4_decode_picture_header(dec_ctx, gb, 0, 1); if (s->width && (!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height)) { ret = ff_set_dimensions(avctx, s->width, s->height); diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c index 34b050db28..ab8d2e8236 100644 --- a/libavcodec/mpeg4videodec.c +++ b/libavcodec/mpeg4videodec.c @@ -2844,7 +2844,8 @@ int ff_mpeg4_workaround_bugs(AVCodecContext *avctx) return 0; } -static int decode_vop_header(Mpeg4DecContext *ctx, GetBitContext *gb) +static int decode_vop_header(Mpeg4DecContext *ctx, GetBitContext *gb, + int parse_only) { MpegEncContext *s = &ctx->m; int time_incr, time_increment; @@ -3018,6 +3019,12 @@ static int decode_vop_header(Mpeg4DecContext *ctx, GetBitContext *gb) ff_init_scantable(s->idsp.idct_permutation, &s->intra_v_scantable, ff_alternate_vertical_scan); } + /* Skip at this point when only parsing since the remaining + * data is not useful for a parser and requires the + * sprite_trajectory VLC to be initialized. */ + if (parse_only) + goto end; + if (s->pict_type == AV_PICTURE_TYPE_S) { if((ctx->vol_sprite_usage == STATIC_SPRITE || ctx->vol_sprite_usage == GMC_SPRITE)) { @@ -3095,6 +3102,8 @@ static int decode_vop_header(Mpeg4DecContext *ctx, GetBitContext *gb) skip_bits(gb, 2); // ref_select_code } } + +end: /* detect buggy encoders which don't set the low_delay flag * (divx4/xvid/opendivx). Note we cannot detect divx5 without B-frames * easily (although it's buggy too) */ @@ -3214,11 +3223,14 @@ static int decode_studiovisualobject(Mpeg4DecContext *ctx, GetBitContext *gb) * Decode MPEG-4 headers. * * @param header If set the absence of a VOP is not treated as error; otherwise, it is treated as such. + * @param parse_only If set, things only relevant to a decoder may be skipped; + * furthermore, the VLC tables may be uninitialized. * @return <0 if an error occurred * FRAME_SKIPPED if a not coded VOP is found * 0 else */ -int ff_mpeg4_decode_picture_header(Mpeg4DecContext *ctx, GetBitContext *gb, int header) +int ff_mpeg4_decode_picture_header(Mpeg4DecContext *ctx, GetBitContext *gb, + int header, int parse_only) { MpegEncContext *s = &ctx->m; unsigned startcode, v; @@ -3371,7 +3383,7 @@ end: } return decode_studio_vop_header(ctx, gb); } else - return decode_vop_header(ctx, gb); + return decode_vop_header(ctx, gb, parse_only); } av_cold void ff_mpeg4videodec_static_init(void) { -- cgit v1.2.3