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

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

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

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

_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel

To unsubscribe, visit link above, or email
ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".