Re: [FFmpeg-devel] [PATCH v1 3/4] avformat/imf: fix packet pts, dts and muxing

[Pierre-Anthony Lemieux <pal@sandflow.com>]

On Sun, Jan 30, 2022 at 2:16 PM Andreas Rheinhardt
<andreas.rheinhardt@outlook.com> wrote:
>
> pal@sandflow.com:
> > From: Pierre-Anthony Lemieux <pal@palemieux.com>
> >
> > The IMF demuxer does not set the DTS and PTS of packets accurately in all
> > scenarios. Moreover, audio packets are not trimmed when they exceed the
> > duration of the underlying resource.
> >
> > Closes https://trac.ffmpeg.org/ticket/9611
> >
> > ---
> >  libavformat/imfdec.c | 225 +++++++++++++++++++++++++------------------
> >  1 file changed, 132 insertions(+), 93 deletions(-)
> >
> > diff --git a/libavformat/imfdec.c b/libavformat/imfdec.c
> > index 6b50b582f6..05dcb6ff31 100644
> > --- a/libavformat/imfdec.c
> > +++ b/libavformat/imfdec.c
> > @@ -65,6 +65,7 @@
> >  #include "avio_internal.h"
> >  #include "imf.h"
> >  #include "internal.h"
> > +#include "libavcodec/packet.h"
> >  #include "libavutil/avstring.h"
> >  #include "libavutil/bprint.h"
> >  #include "libavutil/opt.h"
> > @@ -97,6 +98,9 @@ typedef struct IMFVirtualTrackResourcePlaybackCtx {
> >      IMFAssetLocator *locator;
> >      FFIMFTrackFileResource *resource;
> >      AVFormatContext *ctx;
> > +    AVRational start_time;
> > +    AVRational end_time;
> > +    AVRational ts_offset;
> >  } IMFVirtualTrackResourcePlaybackCtx;
> >
> >  typedef struct IMFVirtualTrackPlaybackCtx {
> > @@ -108,7 +112,6 @@ typedef struct IMFVirtualTrackPlaybackCtx {
> >      IMFVirtualTrackResourcePlaybackCtx *resources; /**< Buffer holding the resources */
> >      int32_t current_resource_index;                /**< Index of the current resource in resources,
> >                                                          or < 0 if a current resource has yet to be selected */
> > -    int64_t last_pts;                              /**< Last timestamp */
> >  } IMFVirtualTrackPlaybackCtx;
> >
> >  typedef struct IMFContext {
> > @@ -342,6 +345,7 @@ static int open_track_resource_context(AVFormatContext *s,
> >      int ret = 0;
> >      int64_t entry_point;
> >      AVDictionary *opts = NULL;
> > +    AVStream *st;
> >
> >      if (track_resource->ctx) {
> >          av_log(s,
> > @@ -383,23 +387,28 @@ static int open_track_resource_context(AVFormatContext *s,
> >      }
> >      av_dict_free(&opts);
> >
> > -    /* Compare the source timebase to the resource edit rate,
> > -     * considering the first stream of the source file
> > -     */
> > -    if (av_cmp_q(track_resource->ctx->streams[0]->time_base,
> > -                 av_inv_q(track_resource->resource->base.edit_rate)))
> > +    /* make sure there is only one stream in the file */
> > +
> > +    if (track_resource->ctx->nb_streams != 1) {
> > +        ret = AVERROR_INVALIDDATA;
> > +        goto cleanup;
> > +    }
> > +
> > +    st = track_resource->ctx->streams[0];
> > +
> > +    /* Warn if the resource time base does not match the file time base */
> > +    if (av_cmp_q(st->time_base, av_inv_q(track_resource->resource->base.edit_rate)))
> >          av_log(s,
> >                 AV_LOG_WARNING,
> > -               "Incoherent source stream timebase %d/%d regarding resource edit rate: %d/%d",
> > -               track_resource->ctx->streams[0]->time_base.num,
> > -               track_resource->ctx->streams[0]->time_base.den,
> > +               "Incoherent source stream timebase " AVRATIONAL_FORMAT
> > +               "regarding resource edit rate: " AVRATIONAL_FORMAT,
> > +               st->time_base.num,
> > +               st->time_base.den,
> >                 track_resource->resource->base.edit_rate.den,
> >                 track_resource->resource->base.edit_rate.num);
> >
> > -    entry_point = (int64_t)track_resource->resource->base.entry_point
> > -        * track_resource->resource->base.edit_rate.den
> > -        * AV_TIME_BASE
> > -        / track_resource->resource->base.edit_rate.num;
> > +    entry_point = av_rescale_q(track_resource->resource->base.entry_point, st->time_base,
> > +                               av_inv_q(track_resource->resource->base.edit_rate));
> >
> >      if (entry_point) {
> >          av_log(s,
> > @@ -407,7 +416,7 @@ static int open_track_resource_context(AVFormatContext *s,
> >                 "Seek at resource %s entry point: %" PRIu32 "\n",
> >                 track_resource->locator->absolute_uri,
> >                 track_resource->resource->base.entry_point);
> > -        ret = avformat_seek_file(track_resource->ctx, -1, entry_point, entry_point, entry_point, 0);
> > +        ret = avformat_seek_file(track_resource->ctx, 0, entry_point, entry_point, entry_point, 0);
> >          if (ret < 0) {
> >              av_log(s,
> >                     AV_LOG_ERROR,
> > @@ -470,11 +479,16 @@ static int open_track_file_resource(AVFormatContext *s,
> >          vt_ctx.locator = asset_locator;
> >          vt_ctx.resource = track_file_resource;
> >          vt_ctx.ctx = NULL;
> > -        track->resources[track->resource_count++] = vt_ctx;
> > -        track->duration = av_add_q(track->duration,
> > +        vt_ctx.start_time = track->duration;
> > +        vt_ctx.ts_offset = av_sub_q(vt_ctx.start_time,
> > +                                    av_div_q(av_make_q((int)track_file_resource->base.entry_point, 1),
> > +                                             track_file_resource->base.edit_rate));
> > +        vt_ctx.end_time = av_add_q(track->duration,
> >                                     av_make_q((int)track_file_resource->base.duration
> >                                                   * track_file_resource->base.edit_rate.den,
> >                                               track_file_resource->base.edit_rate.num));
> > +        track->resources[track->resource_count++] = vt_ctx;
> > +        track->duration = vt_ctx.end_time;
> >      }
> >
> >      return 0;
> > @@ -701,11 +715,14 @@ static IMFVirtualTrackPlaybackCtx *get_next_track_with_minimum_timestamp(AVForma
> >      return track;
> >  }
> >
> > -static IMFVirtualTrackResourcePlaybackCtx *get_resource_context_for_timestamp(AVFormatContext *s,
> > -                                                                              IMFVirtualTrackPlaybackCtx *track)
> > +static int get_resource_context_for_timestamp(AVFormatContext *s, IMFVirtualTrackPlaybackCtx *track, IMFVirtualTrackResourcePlaybackCtx **resource)
> >  {
> > -    AVRational edit_unit_duration = av_inv_q(track->resources[0].resource->base.edit_rate);
> > -    AVRational cumulated_duration = av_make_q(0, edit_unit_duration.den);
> > +    *resource = NULL;
> > +
> > +    if (av_cmp_q(track->current_timestamp, track->duration) >= 0) {
> > +        av_log(s, AV_LOG_DEBUG, "Reached the end of the virtual track\n");
> > +        return AVERROR_EOF;
> > +    }
> >
> >      av_log(s,
> >             AV_LOG_DEBUG,
> > @@ -714,119 +731,141 @@ static IMFVirtualTrackResourcePlaybackCtx *get_resource_context_for_timestamp(AV
> >             av_q2d(track->current_timestamp),
> >             av_q2d(track->duration));
> >      for (uint32_t i = 0; i < track->resource_count; ++i) {
> > -        cumulated_duration = av_add_q(cumulated_duration,
> > -                                      av_make_q((int)track->resources[i].resource->base.duration
> > -                                                    * edit_unit_duration.num,
> > -                                                edit_unit_duration.den));
> >
> > -        if (av_cmp_q(av_add_q(track->current_timestamp, edit_unit_duration), cumulated_duration) <= 0) {
> > +        if (av_cmp_q(track->resources[i].end_time, track->current_timestamp) > 0) {
> >              av_log(s,
> >                     AV_LOG_DEBUG,
> > -                   "Found resource %d in track %d to read for timestamp %lf "
> > -                   "(on cumulated=%lf): entry=%" PRIu32
> > +                   "Found resource %d in track %d to read at timestamp %lf: "
> > +                   "entry=%" PRIu32
> >                     ", duration=%" PRIu32
> > -                   ", editrate=" AVRATIONAL_FORMAT
> > -                   " | edit_unit_duration=%lf\n",
> > +                   ", editrate=" AVRATIONAL_FORMAT,
> >                     i,
> >                     track->index,
> >                     av_q2d(track->current_timestamp),
> > -                   av_q2d(cumulated_duration),
> >                     track->resources[i].resource->base.entry_point,
> >                     track->resources[i].resource->base.duration,
> > -                   AVRATIONAL_ARG(track->resources[i].resource->base.edit_rate),
> > -                   av_q2d(edit_unit_duration));
> > +                   AVRATIONAL_ARG(track->resources[i].resource->base.edit_rate));
> >
> >              if (track->current_resource_index != i) {
> > +                int ret;
> > +
> >                  av_log(s,
> >                         AV_LOG_DEBUG,
> >                         "Switch resource on track %d: re-open context\n",
> >                         track->index);
> > -                if (open_track_resource_context(s, &(track->resources[i])) != 0)
> > -                    return NULL;
> > +
> > +                ret = open_track_resource_context(s, &(track->resources[i]));
> > +                if (ret != 0)
> > +                    return ret;
> >                  if (track->current_resource_index > 0)
> >                      avformat_close_input(&track->resources[track->current_resource_index].ctx);
> >                  track->current_resource_index = i;
> >              }
> >
> > -            return &(track->resources[track->current_resource_index]);
> > +            *resource = &(track->resources[track->current_resource_index]);
> > +            return 0;
> >          }
> >      }
> > -    return NULL;
> > +
> > +    av_log(s, AV_LOG_ERROR, "Could not find IMF track resource to read\n");
> > +    return AVERROR_STREAM_NOT_FOUND;
> > +}
> > +
> > +static int imf_time_to_ts(int64_t *ts, AVRational t, AVRational time_base)
> > +{
> > +    int dst_num;
> > +    int dst_den;
> > +    AVRational r;
> > +
> > +    r = av_div_q(t, time_base);
> > +
> > +    if ((av_reduce(&dst_num, &dst_den, r.num, r.den, INT64_MAX) != 1))
> > +        return 0;
> > +
> > +    if (dst_den != 1)
> > +        return 0;
> > +
> > +    *ts = dst_num;
> > +
> > +    return 1;
> >  }
> >
> >  static int imf_read_packet(AVFormatContext *s, AVPacket *pkt)
> >  {
> > -    IMFContext *c = s->priv_data;
> > -    IMFVirtualTrackResourcePlaybackCtx *resource_to_read = NULL;
> > -    AVRational edit_unit_duration;
> > +    IMFVirtualTrackResourcePlaybackCtx *resource = NULL;
> >      int ret = 0;
> >      IMFVirtualTrackPlaybackCtx *track;
> > -    FFStream *track_stream;
> > +    int64_t delta_ts;
> > +    AVStream *st;
> > +    AVRational next_timestamp;
> >
> >      track = get_next_track_with_minimum_timestamp(s);
> >
> > -    if (av_cmp_q(track->current_timestamp, track->duration) == 0)
> > -        return AVERROR_EOF;
> > +    ret = get_resource_context_for_timestamp(s, track, &resource);
> > +    if (ret)
> > +        return ret;
> >
> > -    resource_to_read = get_resource_context_for_timestamp(s, track);
> > +    ret = av_read_frame(resource->ctx, pkt);
> > +    if (ret) {
> > +        av_log(s, AV_LOG_ERROR, "Failed to read frame\n");
> > +        return ret;
> > +    }
> >
> > -    if (!resource_to_read) {
> > -        edit_unit_duration
> > -            = av_inv_q(track->resources[track->current_resource_index].resource->base.edit_rate);
> > +    av_log(s, AV_LOG_DEBUG, "Got packet: pts=%" PRId64 ", dts=%" PRId64
> > +            ", duration=%" PRId64 ", stream_index=%d, pos=%" PRId64
> > +            ", time_base=" AVRATIONAL_FORMAT "\n", pkt->pts, pkt->dts, pkt->duration,
> > +            pkt->stream_index, pkt->pos, pkt->time_base.num, pkt->time_base.den);
> >
> > -        if (av_cmp_q(av_add_q(track->current_timestamp, edit_unit_duration), track->duration) > 0)
> > -            return AVERROR_EOF;
> > +    /* IMF resources contain only one stream */
> >
> > -        av_log(s, AV_LOG_ERROR, "Could not find IMF track resource to read\n");
> > -        return AVERROR_STREAM_NOT_FOUND;
> > -    }
> > +    if (pkt->stream_index != 0)
> > +        return AVERROR_INVALIDDATA;
> > +    st = resource->ctx->streams[0];
> >
> > -    while (!ff_check_interrupt(c->interrupt_callback) && !ret) {
> > -        ret = av_read_frame(resource_to_read->ctx, pkt);
> > -        av_log(s,
> > -               AV_LOG_DEBUG,
> > -               "Got packet: pts=%" PRId64
> > -               ", dts=%" PRId64
> > -               ", duration=%" PRId64
> > -               ", stream_index=%d, pos=%" PRId64
> > -               "\n",
> > -               pkt->pts,
> > -               pkt->dts,
> > -               pkt->duration,
> > -               pkt->stream_index,
> > -               pkt->pos);
> > -
> > -        track_stream = ffstream(s->streams[track->index]);
> > -        if (ret >= 0) {
> > -            /* Update packet info from track */
> > -            if (pkt->dts < track_stream->cur_dts && track->last_pts > 0)
> > -                pkt->dts = track_stream->cur_dts;
> > -
> > -            pkt->pts = track->last_pts;
> > -            pkt->dts = pkt->dts
> > -                - (int64_t)track->resources[track->current_resource_index].resource->base.entry_point;
> > -            pkt->stream_index = track->index;
> > -
> > -            /* Update track cursors */
> > -            track->current_timestamp
> > -                = av_add_q(track->current_timestamp,
> > -                           av_make_q((int)pkt->duration
> > -                                         * resource_to_read->ctx->streams[0]->time_base.num,
> > -                                     resource_to_read->ctx->streams[0]->time_base.den));
> > -            track->last_pts += pkt->duration;
> > +    pkt->stream_index = track->index;
> >
> > -            return 0;
> > -        } else if (ret != AVERROR_EOF) {
> > -            av_log(s,
> > -                   AV_LOG_ERROR,
> > -                   "Could not get packet from track %d: %s\n",
> > -                   track->index,
> > -                   av_err2str(ret));
> > -            return ret;
> > +    /* adjust the packet PTS and DTS based on the temporal position of the resource within the timeline */
> > +
> > +    if ((imf_time_to_ts(&delta_ts, resource->ts_offset, st->time_base) == 0))
> > +        av_log(s, AV_LOG_WARNING, "Incoherent time stamp " AVRATIONAL_FORMAT " for time base " AVRATIONAL_FORMAT,
> > +               resource->ts_offset.num, resource->ts_offset.den, pkt->time_base.num,
> > +               pkt->time_base.den);
> > +    if (pkt->pts != AV_NOPTS_VALUE)
> > +        pkt->pts += delta_ts;
> > +    if (pkt->dts != AV_NOPTS_VALUE)
> > +        pkt->dts += delta_ts;
> > +
> > +    /* advance the track timestamp by the packet duration */
> > +
> > +    next_timestamp = av_add_q(track->current_timestamp,
> > +                              av_mul_q(av_make_q((int)pkt->duration, 1), st->time_base));
> > +
> > +    /* if necessary, clamp the next timestamp to the end of the current resource */
> > +
> > +    if (av_cmp_q(next_timestamp, resource->end_time) > 0) {
> > +
> > +        next_timestamp = resource->end_time;
> > +
> > +        /* shrink the packet duration */
> > +
> > +        if ((imf_time_to_ts(&pkt->duration, av_sub_q(resource->end_time, track->current_timestamp), st->time_base) == 0))
> > +            av_log(s, AV_LOG_WARNING, "Incoherent time base during packet duration calculation");
> > +
> > +        /* shrink the packet size itself for audio samples */
> > +        /* only AV_CODEC_ID_PCM_S24LE is supported in IMF */
> > +
> > +        if (st->codecpar->codec_id == AV_CODEC_ID_PCM_S24LE) {
> > +            int bytes_per_sample = av_get_exact_bits_per_sample(st->codecpar->codec_id) >> 3;
> > +            int64_t nbsamples = av_rescale_q(pkt->duration, st->time_base, av_make_q(1, st->codecpar->sample_rate));
> > +            av_shrink_packet(pkt, nbsamples * st->codecpar->channels * bytes_per_sample);
> > +        } else {
> > +            av_log(s, AV_LOG_WARNING, "Cannot shrink packets for non-PCM essence");
>
> AV_PKT_DATA_SKIP_SAMPLES

Ok. Would the "reason for end skip" be 1 (convergence)?

>
> >          }
> >      }
> >
> > -    return AVERROR_EOF;
> > +    track->current_timestamp = next_timestamp;
> > +
> > +    return 0;
> >  }
> >
> >  static int imf_close(AVFormatContext *s)
>
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