avformat/imf: fix packet pts, dts and muxing

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.

imf-cpl-with-repeat FATE ref file is regenerated.

Addresses https://trac.ffmpeg.org/ticket/9611

2 files changed, 181 insertions, 102 deletions

diff --git a/libavformat/imfdec.c b/libavformat/imfdec.c
index 48bd5c78e8..bd1135e2e4 100644
--- a/libavformat/imfdec.c
+++ b/libavformat/imfdec.c
@@ -65,8 +65,10 @@
 #include "avio_internal.h"
 #include "imf.h"
 #include "internal.h"
+#include "libavcodec/packet.h"
 #include "libavutil/avstring.h"
 #include "libavutil/bprint.h"
+#include "libavutil/intreadwrite.h"
 #include "libavutil/opt.h"
 #include "mxf.h"
 #include "url.h"
@@ -97,6 +99,9 @@ typedef struct IMFVirtualTrackResourcePlaybackCtx {
     IMFAssetLocator *locator;
     FFIMFTrackFileResource *resource;
     AVFormatContext *ctx;
+    AVRational start_time;
+    AVRational end_time;
+    AVRational ts_offset;
 } IMFVirtualTrackResourcePlaybackCtx;
 
 typedef struct IMFVirtualTrackPlaybackCtx {
@@ -108,7 +113,6 @@ 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 +346,7 @@ 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 +388,28 @@ 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 +417,7 @@ 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 +480,16 @@ 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 +716,14 @@ 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 +732,180 @@ 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 1;
+
+    if (dst_den != 1)
+        return 1;
+
+    *ts = dst_num;
+
+    return 0;
 }
 
 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];
+
+    pkt->stream_index = track->index;
+
+    /* adjust the packet PTS and DTS based on the temporal position of the resource within the timeline */
+
+    ret = imf_time_to_ts(&delta_ts, resource->ts_offset, st->time_base);
+
+    if (!ret) {
+        if (pkt->pts != AV_NOPTS_VALUE)
+            pkt->pts += delta_ts;
+        if (pkt->dts != AV_NOPTS_VALUE)
+            pkt->dts += delta_ts;
+    } else {
+        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);
     }
 
-    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;
+    /* advance the track timestamp by the packet duration */
 
-            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;
+    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) {
+
+        int64_t new_pkt_dur;
+
+        /* shrink the packet duration */
+
+        ret = imf_time_to_ts(&new_pkt_dur,
+                             av_sub_q(resource->end_time, track->current_timestamp),
+                             st->time_base);
+
+        if (!ret)
+            pkt->duration = new_pkt_dur;
+        else
+            av_log(s, AV_LOG_WARNING, "Incoherent time base in packet duration calculation");
+
+        /* shrink the packet itself for audio essence */
+
+        if (st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
+
+            if (st->codecpar->codec_id == AV_CODEC_ID_PCM_S24LE) {
+                /* AV_CODEC_ID_PCM_S24LE is the only PCM format supported in IMF */
+                /* in this case, explicitly shrink the packet */
+
+                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 {
+                /* in all other cases, use side data to skip samples */
+                int64_t skip_samples;
+
+                ret = imf_time_to_ts(&skip_samples,
+                                     av_sub_q(next_timestamp, resource->end_time),
+                                     av_make_q(1, st->codecpar->sample_rate));
+
+                if (ret || skip_samples < 0 || skip_samples > UINT32_MAX) {
+                    av_log(s, AV_LOG_WARNING, "Cannot skip audio samples");
+                } else {
+                    uint8_t *side_data = av_packet_new_side_data(pkt, AV_PKT_DATA_SKIP_SAMPLES, 10);
+                    if (!side_data)
+                        return AVERROR(ENOMEM);
+
+                    AV_WL32(side_data + 4, skip_samples); /* skip from end of this packet */
+                    side_data[6] = 1;                     /* reason for end is convergence */
+                }
+            }
+
+            next_timestamp = resource->end_time;
+
+        } else {
+            av_log(s, AV_LOG_WARNING, "Non-audio packet duration reduced");
         }
     }
 
-    return AVERROR_EOF;
+    track->current_timestamp = next_timestamp;
+
+    return 0;
 }
 
 static int imf_close(AVFormatContext *s)
diff --git a/tests/ref/fate/imf-cpl-with-repeat b/tests/ref/fate/imf-cpl-with-repeat
index fe3106d5c6..e5b3992d04 100644
--- a/tests/ref/fate/imf-cpl-with-repeat
+++ b/tests/ref/fate/imf-cpl-with-repeat
@@ -34,13 +34,13 @@
 0,         28,         28,        1,     1964, 0x106d867a
 0,         29,         29,        1,     1964, 0x106d867a
 0,         30,         30,        1,     1964, 0x106d867a
-0,         30,         31,        1,     2068, 0xd411c582
-0,         30,         32,        1,     2520, 0x7b539dfc
-0,         30,         33,        1,     1846, 0x9d184658
-0,         30,         34,        1,     2475, 0x2967a123
-0,         30,         35,        1,     2540, 0xdc61ad87
-0,         30,         36,        1,     2214, 0xa7da105f
-0,         30,         37,        1,     2486, 0xa68d89b4
-0,         30,         38,        1,     2615, 0xbc35d5ad
-0,         30,         39,        1,     2150, 0x643aea98
-0,         30,         40,        1,     2628, 0x2880c4ad
+0,         31,         31,        1,     2068, 0xd411c582
+0,         32,         32,        1,     2520, 0x7b539dfc
+0,         33,         33,        1,     1846, 0x9d184658
+0,         34,         34,        1,     2475, 0x2967a123
+0,         35,         35,        1,     2540, 0xdc61ad87
+0,         36,         36,        1,     2214, 0xa7da105f
+0,         37,         37,        1,     2486, 0xa68d89b4
+0,         38,         38,        1,     2615, 0xbc35d5ad
+0,         39,         39,        1,     2150, 0x643aea98
+0,         40,         40,        1,     2628, 0x2880c4ad