On 8/6/2020 5:04 AM, Xu Guangxin wrote:
> It's defined in Section 5.2, used by netflix.
> see http://download.opencontent.netflix.com/?prefix=AV1/Chimera/
> ---
> libavformat/allformats.c | 1 +
> libavformat/av1dec.c | 193 +++++++++++++++++++++++++++++++++++++--
> 2 files changed, 185 insertions(+), 9 deletions(-)
>
> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
> index fd9e46e233..8eead5619d 100644
> --- a/libavformat/allformats.c
> +++ b/libavformat/allformats.c
> @@ -75,6 +75,7 @@ extern AVOutputFormat ff_asf_stream_muxer;
> extern AVInputFormat ff_au_demuxer;
> extern AVOutputFormat ff_au_muxer;
> extern AVInputFormat ff_av1_demuxer;
> +extern AVInputFormat ff_av1_low_overhead_demuxer;
How about ff_obu_demuxer instead?
> extern AVInputFormat ff_avi_demuxer;
> extern AVOutputFormat ff_avi_muxer;
> extern AVInputFormat ff_avisynth_demuxer;
> diff --git a/libavformat/av1dec.c b/libavformat/av1dec.c
> index ec66152e03..0c5d172a0f 100644
> --- a/libavformat/av1dec.c
> +++ b/libavformat/av1dec.c
> @@ -28,6 +28,9 @@
> #include "avio_internal.h"
> #include "internal.h"
>
> +//2 + max leb 128 size
> +#define MAX_HEAD_SIZE 10
This value is also used in av1_parse.h, so you could put it there and
reuse it. But if you do, use a less generic name, like MAX_OBU_HEADER_SIZE.
> +
> typedef struct AnnexBContext {
> const AVClass *class;
> AVBSFContext *bsf;
> @@ -139,9 +142,8 @@ 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 *c)
Since c is now a log context, rename it to logctx.
> {
> - AnnexBContext *c = s->priv_data;
> const AVBitStreamFilter *filter = av_bsf_get_by_name("av1_frame_merge");
> AVStream *st;
> int ret;
> @@ -160,25 +162,32 @@ 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 it requires this bsf, then it should be added as a depencency to
configure.
> 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)
> @@ -246,12 +255,158 @@ static int annexb_read_close(AVFormatContext *s)
> return 0;
> }
>
> -#define OFFSET(x) offsetof(AnnexBContext, x)
> +typedef struct LowOverheadContext {
> + const AVClass *class;
> + AVBSFContext *bsf;
> + AVRational framerate;
> + uint8_t prefetched[MAX_HEAD_SIZE];
> + //prefetched len
> + int len;
> +} LowOverheadContext;
> +
> +static int low_overhead_probe(const AVProbeData *p)
> +{
> + AVIOContext pb;
> + int64_t obu_size;
> + int ret, type, cnt = 0, has_size_flag;
> +
> + ffio_init_context(&pb, p->buf, p->buf_size, 0,
> + NULL, NULL, NULL, NULL);
> +
> + // Check that the first OBU is a Temporal Delimiter.
> + ret = read_obu(p->buf + cnt, FFMIN(p->buf_size - cnt, MAX_HEAD_SIZE),
> &obu_size, &type, &has_size_flag);
cnt is 0 at this point, so might as well remove it.
> + if (ret < 0 || type != AV1_OBU_TEMPORAL_DELIMITER || obu_size != 0 ||
> !has_size_flag)
> + return 0;
> + cnt += ret;
> +
> + ret = read_obu(p->buf + cnt, FFMIN(p->buf_size - cnt, MAX_HEAD_SIZE),
> &obu_size, &type, &has_size_flag);
> + if (ret < 0 || type != AV1_OBU_SEQUENCE_HEADER || !has_size_flag)
Afaik, there's nothing in the spec that forbids a Metadata OBU to appear
here before a Sequence Header.
> + return 0;
> + cnt += ret;
> +
> + ret = read_obu(p->buf + cnt, FFMIN(p->buf_size - cnt, MAX_HEAD_SIZE),
> &obu_size, &type, &has_size_flag);
> + if (ret < 0 || (type != AV1_OBU_FRAME && type != AV1_OBU_FRAME_HEADER)
> || obu_size <= 0 || !has_size_flag)
Similarly, the third OBU is not required to be a Frame or Frame Header.
It could be Metadata after the second one was a Sequence Header, or
vice-versa.
> + return 0;
> + return AVPROBE_SCORE_EXTENSION + 1;
> +}
> +
> +static int low_overhead_read_header(AVFormatContext *s)
> +{
> + LowOverheadContext *c = s->priv_data;
> + return read_header(s, c->framerate, &c->bsf, c);
> +}
> +
> +static int low_overhead_prefetch(AVFormatContext *s)
> +{
> + LowOverheadContext *c = s->priv_data;
> + int ret;
> + int size = MAX_HEAD_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 low_overhead_read_data(AVFormatContext *s, AVPacket *pkt, int
> size)
> +{
> + int left;
> + LowOverheadContext *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;
> + memcpy(c->prefetched, c->prefetched + size, left);
This looks like it should be a memmove, as it can overlap.
> + 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 low_overhead_get_packet(AVFormatContext *s, AVPacket *pkt)
> +{
> + int64_t obu_size;
> + int ret, type, has_size_flag;
> + LowOverheadContext *c = s->priv_data;
> + ret = low_overhead_prefetch(s);
> + if (ret < 0)
> + return ret;
> + if (ret) {
> + ret = read_obu(c->prefetched, c->len, &obu_size, &type,
> &has_size_flag);
> + if (ret < 0 && !has_size_flag) {
Shouldn't this be (ret < 0 || !has_size_flag)?
> + av_log(c, AV_LOG_ERROR, "Failed to read obu\n");
> + return ret;
> + }
> + ret = low_overhead_read_data(s, pkt, ret);
> + }
> + return ret;
> +}
> +
> +static int low_overhead_read_packet(AVFormatContext *s, AVPacket *pkt)
> +{
> + LowOverheadContext *c = s->priv_data;
> + int ret;
> +
> + while (1) {
> + ret = low_overhead_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 low_overhead_read_close(AVFormatContext *s)
> +{
> + LowOverheadContext *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(LowOverheadContext, x)
> +static const AVOption low_overhead_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",
> @@ -272,3 +427,23 @@ AVInputFormat ff_av1_demuxer = {
> .flags = AVFMT_GENERIC_INDEX,
> .priv_class = &annexb_demuxer_class,
> };
> +
> +static const AVClass low_overhead_demuxer_class = {
> + .class_name = "AV1 low overhead OBU demuxer",
> + .item_name = av_default_item_name,
> + .option = low_overhead_options,
> + .version = LIBAVUTIL_VERSION_INT,
> +};
> +
> +AVInputFormat ff_av1_low_overhead_demuxer = {
> + .name = "av1",
This name is already used by the AnnexB demuxer, so change it to "obu".
> + .long_name = NULL_IF_CONFIG_SMALL("AV1 low overhead OBU"),
> + .priv_data_size = sizeof(LowOverheadContext),
> + .read_probe = low_overhead_probe,
> + .read_header = low_overhead_read_header,
> + .read_packet = low_overhead_read_packet,
> + .read_close = low_overhead_read_close,
> + .extensions = "obu",
> + .flags = AVFMT_GENERIC_INDEX,
> + .priv_class = &low_overhead_demuxer_class,
> +};
>
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