[FFmpeg-devel] [PATCH 2/2 v2] avformat/movenc: parse h264 packets to build Sync Sample and Recovery Point tables
Andreas Rheinhardt
andreas.rheinhardt at outlook.com
Fri Jul 30 03:49:27 EEST 2021
James Almer:
> Since we can't blindly trust the keyframe flag in packets and assume its
> contents are a valid Sync Sample, do some basic bitstream parsing to build the
> Sync Sample table in addition to a Random Access Recovery Point table.
>
> Suggested-by: ffmpeg at fb.com
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
> libavformat/movenc.c | 142 +++++++++++++++++++++++++++++++++--
> libavformat/movenc.h | 1 +
> tests/ref/lavf-fate/h264.mp4 | 6 +-
> 3 files changed, 139 insertions(+), 10 deletions(-)
>
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index fedc9c0e18..01ab2f43a6 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -34,13 +34,17 @@
> #include "avc.h"
> #include "libavcodec/ac3_parser_internal.h"
> #include "libavcodec/dnxhddata.h"
> +#include "libavcodec/h264.h"
> +#include "libavcodec/h2645_parse.h"
> #include "libavcodec/flac.h"
> #include "libavcodec/get_bits.h"
> +#include "libavcodec/golomb.h"
>
> #include "libavcodec/internal.h"
> #include "libavcodec/put_bits.h"
> #include "libavcodec/vc1_common.h"
> #include "libavcodec/raw.h"
> +#include "libavcodec/sei.h"
> #include "internal.h"
> #include "libavutil/avstring.h"
> #include "libavutil/channel_layout.h"
> @@ -2537,7 +2541,9 @@ static int mov_preroll_write_stbl_atoms(AVIOContext *pb, MOVTrack *track)
> if (!sgpd_entries)
> return AVERROR(ENOMEM);
>
> - av_assert0(track->par->codec_id == AV_CODEC_ID_OPUS || track->par->codec_id == AV_CODEC_ID_AAC);
> + av_assert0(track->par->codec_id == AV_CODEC_ID_OPUS ||
> + track->par->codec_id == AV_CODEC_ID_AAC ||
> + track->par->codec_id == AV_CODEC_ID_H264);
>
> if (track->par->codec_id == AV_CODEC_ID_OPUS) {
> for (i = 0; i < track->entry; i++) {
> @@ -2566,6 +2572,18 @@ static int mov_preroll_write_stbl_atoms(AVIOContext *pb, MOVTrack *track)
> sgpd_entries[entries].group_description_index = distance ? ++group : 0;
> }
> }
> + } else if (track->par->codec_id == AV_CODEC_ID_H264) {
> + for (i = 0; i < track->entry; i++) {
> + int distance = track->cluster[i].roll_distance;
> + if (i && distance == sgpd_entries[entries].roll_distance) {
> + sgpd_entries[entries].count++;
> + } else {
> + entries++;
> + sgpd_entries[entries].count = 1;
> + sgpd_entries[entries].roll_distance = distance;
> + sgpd_entries[entries].group_description_index = distance ? ++group : 0;
> + }
> + }
> } else {
> entries++;
> sgpd_entries[entries].count = track->sample_count;
> @@ -2639,7 +2657,9 @@ static int mov_write_stbl_tag(AVFormatContext *s, AVIOContext *pb, MOVMuxContext
> if (track->cenc.aes_ctr) {
> ff_mov_cenc_write_stbl_atoms(&track->cenc, pb);
> }
> - if (track->par->codec_id == AV_CODEC_ID_OPUS || track->par->codec_id == AV_CODEC_ID_AAC) {
> + if (track->par->codec_id == AV_CODEC_ID_OPUS ||
> + track->par->codec_id == AV_CODEC_ID_AAC ||
> + track->par->codec_id == AV_CODEC_ID_H264) {
> mov_preroll_write_stbl_atoms(pb, track);
> }
> return update_size(pb, pos);
> @@ -5150,6 +5170,107 @@ static int mov_parse_mpeg2_frame(AVPacket *pkt, uint32_t *flags)
> return 0;
> }
>
> +static int mov_parse_h264_frame(AVPacket *pkt, MOVTrack *trk, uint8_t *reformatted_data,
> + int size)
> +{
> + const uint8_t *buf, *buf_end, *sei_buf = NULL;
> + uint32_t state = -1;
> + unsigned roll_distance = 0;
> + int nal_length_size = 0, nalsize;
> + int ret, idr = 0;
> +
> + if (!size)
> + return 0;
> + if (trk->vos_data && trk->vos_data[0] == 1) {
> + if (trk->vos_len < 5)
> + return 0;
> + nal_length_size = (trk->vos_data[4] & 0x03) + 1;
> + buf = pkt->data;
> + buf_end = pkt->data + size;
> + } else {
> + nal_length_size = 4;
> + buf = reformatted_data;
> + buf_end = reformatted_data + size;
> + }
> +
> + while (buf_end - buf >= 4) {
> + int i = 0;
This variable can use case H264_NAL_SEI scope.
> + nalsize = get_nalsize(nal_length_size, buf, buf_end - buf, &i, NULL);
> + if (nalsize < 0)
> + break;
> + state = buf[nal_length_size];
> + buf += nal_length_size + 1;
> + nalsize--;
> +
> + switch (state & 0x1f) {
> + case H264_NAL_IDR_SLICE:
> + idr = 1;
> + // fall-through
> + case H264_NAL_SLICE:
> + goto end;
Given that you are now only parsing until you have the first VLC slice I
wonder whether it is really advantageous to reuse the already
transformed packet; after all, ff_avc_parse_nal_units_buf() has an
allocation and a memcpy more than ff_avc_parse_nal_units() which
probably outweighs any savings in this function given that SEIs are so tiny.
Maybe the helper function from my old patchset
https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200709191805.21648-1-andreas.rheinhardt@gmail.com/
(which I never pushed because I feared that I was too strict) could be
helpful? (But one would probably have to add a new parameter to allow to
peek into the future (i.e. see what the next NALU will be); otherwise
one would needlessly try to find the end of the first VLC NALU.
> + case H264_NAL_SEI: {
> + int sei_size;
> +
> + sei_buf = ff_nal_unit_extract_rbsp(buf, nalsize, &sei_size, 0);
> + if (!sei_buf)
> + goto end;
> +
> + i = 0;
> + do {
> + GetBitContext gb;
> + int payload_type = 0, payload_size = 0;
> +
> + do {
> + if (sei_size - i < 1)
sei_size <= i seems more natural.
> + goto end;
> + payload_type += sei_buf[i];
> + } while (sei_buf[i++] == 255);
> + do {
> + if (sei_size - i < 1)
> + goto end;
> + payload_size += sei_buf[i];
> + } while (sei_buf[i++] == 255);
> +
> + if (payload_size > sei_size - i)
> + goto end;
> +
> + ret = init_get_bits8(&gb, sei_buf + i, payload_size);
> + if (ret < 0)
> + goto end;
> +
> + switch (payload_type) {
> + case SEI_TYPE_RECOVERY_POINT:
> + roll_distance = get_ue_golomb_long(&gb);
> + break;
> + default:
> + break;
> + }
> + i += payload_size;
> + } while (sei_size - i > 0 && sei_buf[i] != 0x80);
> + av_freep(&sei_buf);
> + break;
> + }
> + default:
> + break;
> + }
> + buf += nalsize;
> + }
> +
> +end:
> + if (roll_distance != (int16_t)roll_distance)
> + roll_distance = 0;
> + trk->cluster[trk->entry].roll_distance = roll_distance;
> +
> + if (idr) {
> + trk->cluster[trk->entry].flags |= MOV_SYNC_SAMPLE;
> + trk->has_keyframes++;
> + }
> +
> + av_freep(&sei_buf);
> +
> + return 0;
> +}
> +
> static void mov_parse_vc1_frame(AVPacket *pkt, MOVTrack *trk)
> {
> const uint8_t *start, *next, *end = pkt->data + pkt->size;
> @@ -5638,13 +5759,17 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
> avio_write(pb, reformatted_data, size);
> } else {
> if (trk->cenc.aes_ctr) {
> - size = ff_mov_cenc_avc_parse_nal_units(&trk->cenc, pb, pkt->data, size);
> - if (size < 0) {
> - ret = size;
> + ret = ff_avc_parse_nal_units_buf(pkt->data, &reformatted_data, &size);
> + if (ret < 0)
> + return ret;
> + ret = ff_mov_cenc_avc_write_nal_units(s, &trk->cenc, 4, pb, reformatted_data, size);
> + if (ret < 0)
> goto err;
> - }
> } else {
> - size = ff_avc_parse_nal_units(pb, pkt->data, pkt->size);
> + ret = ff_avc_parse_nal_units_buf(pkt->data, &reformatted_data, &size);
> + if (ret < 0)
> + return ret;
You can factor the call to ff_avc_parse_nal_units_buf() out; in fact,
not only the two branches seen here do this, but the code immediately
above this does it as well: It even coincides with what is here.
> + avio_write(pb, reformatted_data, size);
> }
> }
> } else if (par->codec_id == AV_CODEC_ID_HEVC && trk->vos_len > 6 &&
> @@ -5740,6 +5865,7 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
> trk->cluster[trk->entry].entries = samples_in_chunk;
> trk->cluster[trk->entry].dts = pkt->dts;
> trk->cluster[trk->entry].pts = pkt->pts;
> + trk->cluster[trk->entry].roll_distance = 0;
> if (!trk->entry && trk->start_dts != AV_NOPTS_VALUE) {
> if (!trk->frag_discont) {
> /* First packet of a new fragment. We already wrote the duration
> @@ -5821,6 +5947,8 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
>
> if (par->codec_id == AV_CODEC_ID_VC1) {
> mov_parse_vc1_frame(pkt, trk);
> + } else if (par->codec_id == AV_CODEC_ID_H264 && !TAG_IS_AVCI(trk->tag)) {
> + mov_parse_h264_frame(pkt, trk, reformatted_data, size);
> } else if (par->codec_id == AV_CODEC_ID_TRUEHD) {
> mov_parse_truehd_frame(pkt, trk);
> } else if (pkt->flags & AV_PKT_FLAG_KEY) {
> diff --git a/libavformat/movenc.h b/libavformat/movenc.h
> index af1ea0bce6..73bf73ce8f 100644
> --- a/libavformat/movenc.h
> +++ b/libavformat/movenc.h
> @@ -56,6 +56,7 @@ typedef struct MOVIentry {
> #define MOV_PARTIAL_SYNC_SAMPLE 0x0002
> #define MOV_DISPOSABLE_SAMPLE 0x0004
> uint32_t flags;
> + int16_t roll_distance;
> AVProducerReferenceTime prft;
> } MOVIentry;
>
> diff --git a/tests/ref/lavf-fate/h264.mp4 b/tests/ref/lavf-fate/h264.mp4
> index a9c3823c2c..c08ee4c7ae 100644
> --- a/tests/ref/lavf-fate/h264.mp4
> +++ b/tests/ref/lavf-fate/h264.mp4
> @@ -1,3 +1,3 @@
> -fe299ea5205b71a48281f917b1256a5d *tests/data/lavf-fate/lavf.h264.mp4
> -547928 tests/data/lavf-fate/lavf.h264.mp4
> -tests/data/lavf-fate/lavf.h264.mp4 CRC=0x9da2c999
> +2812f617314d23474fcb23898b8a56ab *tests/data/lavf-fate/lavf.h264.mp4
> +548084 tests/data/lavf-fate/lavf.h264.mp4
> +tests/data/lavf-fate/lavf.h264.mp4 CRC=0x396f0829
>
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