[FFmpeg-devel] [PATCH V2 2/3] avormat/av1dec: add low-overhead bitstream format
James Almer
jamrial at gmail.com
Wed Aug 12 16:06:16 EEST 2020
On 8/10/2020 6:34 AM, Xu Guangxin wrote:
> It's defined in Section 5.2, used by netflix.
> see http://download.opencontent.netflix.com/?prefix=AV1/Chimera/
> ---
> configure | 1 +
> libavformat/allformats.c | 1 +
> libavformat/av1dec.c | 266 +++++++++++++++++++++++++++++++++++----
> 3 files changed, 245 insertions(+), 23 deletions(-)
>
> diff --git a/configure b/configure
> index 8de1afcb99..d4a1fea9ce 100755
> --- a/configure
> +++ b/configure
> @@ -3331,6 +3331,7 @@ mxf_d10_muxer_select="mxf_muxer"
> mxf_opatom_muxer_select="mxf_muxer"
> nut_muxer_select="riffenc"
> nuv_demuxer_select="riffdec"
> +obu_demuxer_select="av1_frame_merge_bsf av1_parser"
> oga_muxer_select="ogg_muxer"
> ogg_demuxer_select="dirac_parse"
> ogv_muxer_select="ogg_muxer"
> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
> index b7e59ae170..0aa9dd7198 100644
> --- a/libavformat/allformats.c
> +++ b/libavformat/allformats.c
> @@ -293,6 +293,7 @@ extern AVOutputFormat ff_null_muxer;
> extern AVInputFormat ff_nut_demuxer;
> extern AVOutputFormat ff_nut_muxer;
> extern AVInputFormat ff_nuv_demuxer;
> +extern AVInputFormat ff_obu_demuxer;
> extern AVOutputFormat ff_oga_muxer;
> extern AVInputFormat ff_ogg_demuxer;
> extern AVOutputFormat ff_ogg_muxer;
> diff --git a/libavformat/av1dec.c b/libavformat/av1dec.c
> index 1be2fac1c1..14efb8f1d4 100644
> --- a/libavformat/av1dec.c
> +++ b/libavformat/av1dec.c
> @@ -70,6 +70,24 @@ static int read_obu(const uint8_t *buf, int size, int64_t *obu_size, int *type)
> return 0;
> }
>
> +//return < 0 if we need more data
> +static int get_score(int type, int *seq)
> +{
> + switch (type) {
> + case AV1_OBU_SEQUENCE_HEADER:
> + *seq = 1;
> + return -1;
> + case AV1_OBU_FRAME:
> + case AV1_OBU_FRAME_HEADER:
> + return *seq ? AVPROBE_SCORE_EXTENSION + 1 : 0;
> + case AV1_OBU_METADATA:
> + return -1;
> + default:
> + break;
Padding OBU should be ignored/skipped, same as Metadata. This function
should make the caller abort only for OBUs that are not meant to appear
before a Frame/Frame Header (Tile list, Tile Group, Redundant Frame
Header, another Temporal Delimiter).
> + }
> + return 0;
> +}
> +
> static int annexb_probe(const AVProbeData *p)
> {
> AVIOContext pb;
> @@ -123,19 +141,9 @@ static int annexb_probe(const AVProbeData *p)
> return 0;
> cnt += obu_unit_size;
>
> - switch (type) {
> - case AV1_OBU_SEQUENCE_HEADER:
> - seq = 1;
> - break;
> - case AV1_OBU_FRAME:
> - case AV1_OBU_FRAME_HEADER:
> - return seq ? AVPROBE_SCORE_EXTENSION + 1 : 0;
> - case AV1_OBU_TILE_GROUP:
> - case AV1_OBU_TEMPORAL_DELIMITER:
> - return 0;
> - default:
> - break;
> - }
> + ret = get_score(type, &seq);
> + if (ret >= 0)
> + return ret;
>
> temporal_unit_size -= obu_unit_size + ret;
> frame_unit_size -= obu_unit_size + ret;
> @@ -144,15 +152,14 @@ static int annexb_probe(const AVProbeData *p)
> return 0;
> }
>
> -static int annexb_read_header(AVFormatContext *s)
> +static int read_header(AVFormatContext *s, AVRational framerate, AVBSFContext **bsf, void *logctx)
Nit: Maybe a pointer to framerate instead.
> {
> - AnnexBContext *c = s->priv_data;
> const AVBitStreamFilter *filter = av_bsf_get_by_name("av1_frame_merge");
> AVStream *st;
> int ret;
>
> if (!filter) {
> - av_log(c, AV_LOG_ERROR, "av1_frame_merge bitstream filter "
> + av_log(logctx, AV_LOG_ERROR, "av1_frame_merge bitstream filter "
> "not found. This is a bug, please report it.\n");
> return AVERROR_BUG;
> }
> @@ -165,25 +172,32 @@ static int annexb_read_header(AVFormatContext *s)
> st->codecpar->codec_id = AV_CODEC_ID_AV1;
> st->need_parsing = AVSTREAM_PARSE_HEADERS;
>
> - st->internal->avctx->framerate = c->framerate;
> + st->internal->avctx->framerate = framerate;
> // taken from rawvideo demuxers
> avpriv_set_pts_info(st, 64, 1, 1200000);
>
> - ret = av_bsf_alloc(filter, &c->bsf);
> + ret = av_bsf_alloc(filter, bsf);
> if (ret < 0)
> return ret;
>
> - ret = avcodec_parameters_copy(c->bsf->par_in, st->codecpar);
> + ret = avcodec_parameters_copy((*bsf)->par_in, st->codecpar);
> if (ret < 0) {
> - av_bsf_free(&c->bsf);
> + av_bsf_free(bsf);
> return ret;
> }
>
> - ret = av_bsf_init(c->bsf);
> + ret = av_bsf_init(*bsf);
> if (ret < 0)
> - av_bsf_free(&c->bsf);
> + av_bsf_free(bsf);
>
> return ret;
> +
> +}
> +
> +static int annexb_read_header(AVFormatContext *s)
> +{
> + AnnexBContext *c = s->priv_data;
> + return read_header(s, c->framerate, &c->bsf, c);
> }
>
> static int annexb_read_packet(AVFormatContext *s, AVPacket *pkt)
> @@ -251,12 +265,198 @@ static int annexb_read_close(AVFormatContext *s)
> return 0;
> }
>
> -#define OFFSET(x) offsetof(AnnexBContext, x)
> +typedef struct ObuContext {
> + const AVClass *class;
> + AVBSFContext *bsf;
> + AVRational framerate;
> + uint8_t prefetched[MAX_OBU_HEADER_SIZE];
> + //prefetched len
> + int len;
> +} ObuContext;
> +
> +//For low overhead obu, we can't foresee the obu size before we parsed the header.
> +//So, we can't use parse_obu_header here, since it will check size <= buf_size
> +//see c27c7b49dc for more details
> +static int read_obu_with_size(const uint8_t *buf, int buf_size, int64_t *obu_size, int *type)
> +{
> + GetBitContext gb;
> + int ret, extension_flag, start_pos;
> + int64_t size;
> +
> + ret = init_get_bits8(&gb, buf, FFMIN(buf_size, MAX_OBU_HEADER_SIZE));
> + if (ret < 0)
> + return ret;
> +
> + if (get_bits1(&gb) != 0) // obu_forbidden_bit
> + return AVERROR_INVALIDDATA;
> +
> + *type = get_bits(&gb, 4);
> + extension_flag = get_bits1(&gb);
> + if (!get_bits1(&gb)) // has_size_flag
> + return AVERROR_INVALIDDATA;
> + skip_bits1(&gb); // obu_reserved_1bit
> +
> + if (extension_flag) {
> + get_bits(&gb, 3); // temporal_id
> + get_bits(&gb, 2); // spatial_id
> + skip_bits(&gb, 3); // extension_header_reserved_3bits
> + }
> +
> + *obu_size = leb128(&gb);
> + if (*obu_size > INT_MAX)
> + return AVERROR_INVALIDDATA;
> +
> + if (get_bits_left(&gb) < 0)
> + return AVERROR_INVALIDDATA;
> +
> + start_pos = get_bits_count(&gb) / 8;
> +
> + size = *obu_size + start_pos;
> + if (size > INT_MAX)
> + return AVERROR_INVALIDDATA;
> + return size;
> +}
> +
> +static int obu_probe(const AVProbeData *p)
> +{
> + int64_t obu_size;
> + int seq = 0;
> + int ret, type, cnt;
> +
> + // Check that the first OBU is a Temporal Delimiter.
> + cnt = read_obu_with_size(p->buf, p->buf_size, &obu_size, &type);
> + if (cnt < 0 || type != AV1_OBU_TEMPORAL_DELIMITER || obu_size != 0)
> + return 0;
> +
> + while (1) {
> + ret = read_obu_with_size(p->buf + cnt, p->buf_size - cnt, &obu_size, &type);
You need to ensure p->buf_size is bigger than cnt to avoid overreads
when you attempt to skip to the next OBU, so use read_obu() here since
you're passing the entire buffer length and not just up to 10 bytes like
in obu_get_packet() below. The size <= buf_size check is needed here.
> + if (ret < 0 || obu_size <= 0)
> + return 0;
> + cnt += ret;
> +
> + ret = get_score(type, &seq);
> + if (ret >= 0)
> + return ret;
> + }
> + return 0;
> +}
> +
> +static int obu_read_header(AVFormatContext *s)
> +{
> + ObuContext *c = s->priv_data;
> + return read_header(s, c->framerate, &c->bsf, c);
> +}
> +
> +static int obu_prefetch(AVFormatContext *s)
> +{
> + ObuContext *c = s->priv_data;
> + int ret;
> + int size = MAX_OBU_HEADER_SIZE - c->len;
> + if (size > 0 && !avio_feof(s->pb)) {
> + ret = avio_read(s->pb, &c->prefetched[c->len], size);
> + if (ret < 0)
> + return ret;
> + c->len += ret;
> + }
> + return c->len;
> +}
> +
> +static int obu_read_data(AVFormatContext *s, AVPacket *pkt, int size)
> +{
> + int left;
> + ObuContext *c = s->priv_data;
> + int ret = av_new_packet(pkt, size);
> + if (ret < 0) {
> + av_log(c, AV_LOG_ERROR, "Failed to allocate packet for obu\n");
> + return ret;
> + }
> + if (size <= c->len) {
> + memcpy(pkt->data, c->prefetched, size);
> +
> + left = c->len - size;
> + memmove(c->prefetched, c->prefetched + size, left);
You can probably use av_fifo_* functions for the prefetch buffer. See
libavutil/fifo.h
> + c->len = left;
> + } else {
> + memcpy(pkt->data, c->prefetched, c->len);
> + left = size - c->len;
> + ret = avio_read(s->pb, pkt->data + c->len, left);
> + if (ret != left) {
> + av_log(c, AV_LOG_ERROR, "Failed to read %d frome file\n", left);
> + return ret;
> + }
> + c->len = 0;
> + }
> + return 0;
> +}
> +
> +static int obu_get_packet(AVFormatContext *s, AVPacket *pkt)
> +{
> + int64_t obu_size;
> + int ret, type;
> + ObuContext *c = s->priv_data;
> + ret = obu_prefetch(s);
> + if (ret < 0)
> + return ret;
> + if (ret) {
> + ret = read_obu_with_size(c->prefetched, c->len, &obu_size, &type);
> + if (ret < 0) {
> + av_log(c, AV_LOG_ERROR, "Failed to read obu\n");
> + return ret;
> + }
> + ret = obu_read_data(s, pkt, ret);
> + }
> + return ret;
> +}
> +
> +static int obu_read_packet(AVFormatContext *s, AVPacket *pkt)
> +{
> + ObuContext *c = s->priv_data;
> + int ret;
> +
> + while (1) {
> + ret = obu_get_packet(s, pkt);
> + if (ret < 0)
> + return ret;
> + ret = av_bsf_send_packet(c->bsf, pkt);
> + if (ret < 0) {
> + av_log(s, AV_LOG_ERROR, "Failed to send packet to "
> + "av1_frame_merge filter\n");
> + return ret;
> + }
> + ret = av_bsf_receive_packet(c->bsf, pkt);
> + if (ret < 0 && ret != AVERROR(EAGAIN) && ret != AVERROR_EOF)
> + av_log(s, AV_LOG_ERROR, "av1_frame_merge filter failed to "
> + "send output packet\n");
> + if (ret != AVERROR(EAGAIN))
> + break;
> + }
> +
> + return ret;
> +}
> +
> +static int obu_read_close(AVFormatContext *s)
> +{
> + ObuContext *c = s->priv_data;
> +
> + av_bsf_free(&c->bsf);
> + return 0;
> +}
> +
> #define DEC AV_OPT_FLAG_DECODING_PARAM
> +
> +#define OFFSET(x) offsetof(AnnexBContext, x)
> static const AVOption annexb_options[] = {
> { "framerate", "", OFFSET(framerate), AV_OPT_TYPE_VIDEO_RATE, {.str = "25"}, 0, INT_MAX, DEC},
> { NULL },
> };
> +#undef OFFSET
> +
> +#define OFFSET(x) offsetof(ObuContext, x)
> +static const AVOption obu_options[] = {
> + { "framerate", "", OFFSET(framerate), AV_OPT_TYPE_VIDEO_RATE, {.str = "25"}, 0, INT_MAX, DEC},
> + { NULL },
> +};
> +#undef OFFSET
>
> static const AVClass annexb_demuxer_class = {
> .class_name = "AV1 Annex B demuxer",
> @@ -277,3 +477,23 @@ AVInputFormat ff_av1_demuxer = {
> .flags = AVFMT_GENERIC_INDEX,
> .priv_class = &annexb_demuxer_class,
> };
> +
> +static const AVClass obu_demuxer_class = {
> + .class_name = "AV1 low overhead OBU demuxer",
> + .item_name = av_default_item_name,
> + .option = obu_options,
> + .version = LIBAVUTIL_VERSION_INT,
> +};
> +
> +AVInputFormat ff_obu_demuxer = {
> + .name = "obu",
> + .long_name = NULL_IF_CONFIG_SMALL("AV1 low overhead OBU"),
> + .priv_data_size = sizeof(ObuContext),
> + .read_probe = obu_probe,
> + .read_header = obu_read_header,
> + .read_packet = obu_read_packet,
> + .read_close = obu_read_close,
> + .extensions = "obu",
> + .flags = AVFMT_GENERIC_INDEX,
> + .priv_class = &obu_demuxer_class,
> +};
>
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