[FFmpeg-devel] [PATCH v2 3/4] avformat/imf: Demuxer implementation

pal at sandflow.com pal at sandflow.com
Fri Nov 5 00:29:53 EET 2021


From: Pierre-Anthony Lemieux <pal at palemieux.com>

Signed-off-by: Pierre-Anthony Lemieux <pal at palemieux.com>
---

Notes:
    Implements the IMF demuxer.

 libavformat/imfdec.c | 735 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 735 insertions(+)
 create mode 100644 libavformat/imfdec.c

diff --git a/libavformat/imfdec.c b/libavformat/imfdec.c
new file mode 100644
index 0000000000..96272e04d8
--- /dev/null
+++ b/libavformat/imfdec.c
@@ -0,0 +1,735 @@
+/*
+ * Copyright (c) Sandflow Consulting LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * Demuxes an IMF Composition
+ *
+ * References
+ * OV 2067-0:2018 - SMPTE Overview Document - Interoperable Master Format
+ * ST 2067-2:2020 - SMPTE Standard - Interoperable Master Format — Core Constraints
+ * ST 2067-3:2020 - SMPTE Standard - Interoperable Master Format — Composition Playlist
+ * ST 2067-5:2020 - SMPTE Standard - Interoperable Master Format — Essence Component
+ * ST 2067-20:2016 - SMPTE Standard - Interoperable Master Format — Application #2
+ * ST 2067-21:2020 - SMPTE Standard - Interoperable Master Format — Application #2 Extended
+ * ST 2067-102:2017 - SMPTE Standard - Interoperable Master Format — Common Image Pixel Color Schemes
+ * ST 429-9:2007 - SMPTE Standard - D-Cinema Packaging — Asset Mapping and File Segmentation
+ *
+ * @author Marc-Antoine Arnaud
+ * @author Valentin Noel
+ * @file
+ * @ingroup lavu_imf
+ */
+
+#include "imf.h"
+#include "internal.h"
+#include "libavutil/avstring.h"
+#include "libavutil/bprint.h"
+#include "libavutil/opt.h"
+#include "mxf.h"
+#include "url.h"
+#include <inttypes.h>
+#include <libxml/parser.h>
+
+#define MAX_BPRINT_READ_SIZE (UINT_MAX - 1)
+#define DEFAULT_ASSETMAP_SIZE 8 * 1024
+#define IMF_AVRATIONAL_FORMAT "%d/%d"
+#define IMF_AVRATIONAL_ARG(rational) rational.num, rational.den
+
+/**
+ * IMF Asset locator
+ */
+typedef struct IMFAssetLocator {
+    UUID uuid;
+    char *absolute_uri;
+} IMFAssetLocator;
+
+/**
+ * IMF Asset locator map
+ * Results from the parsing of one or more ASSETMAP XML files
+ */
+typedef struct IMFAssetLocatorMap {
+    uint8_t asset_count;
+    IMFAssetLocator **assets;
+} IMFAssetLocatorMap;
+
+typedef struct IMFVirtualTrackResourcePlaybackCtx {
+    IMFAssetLocator *locator;
+    IMFTrackFileResource *resource;
+    AVFormatContext *ctx;
+} IMFVirtualTrackResourcePlaybackCtx;
+
+typedef struct IMFVirtualTrackPlaybackCtx {
+    // Track index in playlist
+    int32_t index;
+    // Time counters
+    AVRational current_timestamp;
+    AVRational duration;
+    // Resources
+    unsigned int resource_count;
+    IMFVirtualTrackResourcePlaybackCtx **resources;
+    // Decoding cursors
+    uint32_t current_resource_index;
+    int64_t last_pts;
+} IMFVirtualTrackPlaybackCtx;
+
+typedef struct IMFContext {
+    const AVClass *class;
+    const char *base_url;
+    char *asset_map_paths;
+    AVIOInterruptCB *interrupt_callback;
+    AVDictionary *avio_opts;
+    IMFCPL *cpl;
+    IMFAssetLocatorMap *asset_locator_map;
+    unsigned int track_count;
+    IMFVirtualTrackPlaybackCtx **tracks;
+} IMFContext;
+
+static int imf_uri_is_url(const char *string)
+{
+    char *substr = strstr(string, "://");
+    return substr != NULL;
+}
+
+static int imf_uri_is_unix_abs_path(const char *string)
+{
+    char *substr = strstr(string, "/");
+    int index = (int)(substr - string);
+    return index == 0;
+}
+
+static int imf_uri_is_dos_abs_path(const char *string)
+{
+    // Absolute path case: `C:\path\to\somwhere`
+    char *substr = strstr(string, ":\\");
+    int index = (int)(substr - string);
+    if (index == 1)
+        return 1;
+
+    // Absolute path case: `C:/path/to/somwhere`
+    substr = strstr(string, ":/");
+    index = (int)(substr - string);
+    if (index == 1)
+        return 1;
+
+    // Network path case: `\\path\to\somwhere`
+    substr = strstr(string, "\\\\");
+    index = (int)(substr - string);
+    return index == 0;
+}
+
+/**
+ * Parse a ASSETMAP XML file to extract the UUID-URI mapping of assets.
+ * @param s the current format context, if any (can be NULL).
+ * @param doc the XML document to be parsed.
+ * @param asset_map pointer on the IMFAssetLocatorMap pointer to fill.
+ * @param base_url the url of the asset map XML file, if any (can be NULL).
+ * @return a negative value in case of error, 0 otherwise.
+ */
+static int parse_imf_asset_map_from_xml_dom(AVFormatContext *s, xmlDocPtr doc, IMFAssetLocatorMap **asset_map, const char *base_url)
+{
+    xmlNodePtr asset_map_element = NULL;
+    xmlNodePtr node = NULL;
+    char *uri;
+    int ret = 0;
+
+    IMFAssetLocator *asset = NULL;
+
+    asset_map_element = xmlDocGetRootElement(doc);
+
+    if (!asset_map_element) {
+        av_log(s, AV_LOG_ERROR, "Unable to parse asset map XML - missing root node\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (asset_map_element->type != XML_ELEMENT_NODE || av_strcasecmp(asset_map_element->name, "AssetMap")) {
+        av_log(s, AV_LOG_ERROR, "Unable to parse asset map XML - wrong root node name[%s] type[%d]\n", asset_map_element->name, (int)asset_map_element->type);
+        return AVERROR_INVALIDDATA;
+    }
+
+    // parse asset locators
+
+    if (!(node = imf_xml_get_child_element_by_name(asset_map_element, "AssetList"))) {
+        av_log(s, AV_LOG_ERROR, "Unable to parse asset map XML - missing AssetList node\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    node = xmlFirstElementChild(node);
+    while (node) {
+        if (av_strcasecmp(node->name, "Asset") != 0) {
+            continue;
+        }
+
+        asset = av_malloc(sizeof(IMFAssetLocator));
+        if (!asset)
+            return AVERROR(ENOMEM);
+
+        if (imf_xml_read_UUID(imf_xml_get_child_element_by_name(node, "Id"), asset->uuid)) {
+            av_log(s, AV_LOG_ERROR, "Could not parse UUID from asset in asset map.\n");
+            av_freep(&asset);
+            return 1;
+        }
+
+        av_log(s, AV_LOG_DEBUG, "Found asset id: " IMF_UUID_FORMAT "\n", UID_ARG(asset->uuid));
+
+        if (!(node = imf_xml_get_child_element_by_name(node, "ChunkList"))) {
+            av_log(s, AV_LOG_ERROR, "Unable to parse asset map XML - missing ChunkList node\n");
+            return AVERROR_INVALIDDATA;
+        }
+
+        if (!(node = imf_xml_get_child_element_by_name(node, "Chunk"))) {
+            av_log(s, AV_LOG_ERROR, "Unable to parse asset map XML - missing Chunk node\n");
+            return AVERROR_INVALIDDATA;
+        }
+
+        uri = xmlNodeGetContent(imf_xml_get_child_element_by_name(node, "Path"));
+        if (!imf_uri_is_url(uri) && !imf_uri_is_unix_abs_path(uri) && !imf_uri_is_dos_abs_path(uri))
+            asset->absolute_uri = av_append_path_component(base_url, uri);
+        else
+            asset->absolute_uri = av_strdup(uri);
+        xmlFree(uri);
+        if (!asset->absolute_uri) {
+            av_log(NULL, AV_LOG_PANIC, "Cannot allocate asset locator absolute URI\n");
+            return AVERROR(ENOMEM);
+        }
+
+        av_log(s, AV_LOG_DEBUG, "Found asset absolute URI: %s\n", asset->absolute_uri);
+
+        node = xmlNextElementSibling(node->parent->parent);
+
+        (*asset_map)->assets = av_realloc((*asset_map)->assets, ((*asset_map)->asset_count + 1) * sizeof(IMFAssetLocator));
+        if (!(*asset_map)->assets) {
+            av_log(NULL, AV_LOG_PANIC, "Cannot allocate IMF asset locators\n");
+            return AVERROR(ENOMEM);
+        }
+        (*asset_map)->assets[(*asset_map)->asset_count++] = asset;
+    }
+
+    return ret;
+}
+
+/**
+ * Allocate a IMFAssetLocatorMap pointer and return it.
+ * @return the allocated IMFAssetLocatorMap pointer.
+ */
+static IMFAssetLocatorMap *imf_asset_locator_map_alloc(void)
+{
+    IMFAssetLocatorMap *asset_map;
+
+    asset_map = av_malloc(sizeof(IMFAssetLocatorMap));
+    if (!asset_map)
+        return NULL;
+
+    asset_map->assets = NULL;
+    asset_map->asset_count = 0;
+    return asset_map;
+}
+
+/**
+ * Free a IMFAssetLocatorMap pointer.
+ */
+static void imf_asset_locator_map_free(IMFAssetLocatorMap *asset_map)
+{
+    if (asset_map == NULL) {
+        return;
+    }
+
+    for (int i = 0; i < asset_map->asset_count; ++i) {
+        av_free(asset_map->assets[i]->absolute_uri);
+        av_free(asset_map->assets[i]);
+    }
+
+    av_freep(&asset_map->assets);
+    av_freep(&asset_map);
+}
+
+static int parse_assetmap(AVFormatContext *s, const char *url, AVIOContext *in)
+{
+    IMFContext *c = s->priv_data;
+    struct AVBPrint buf;
+    AVDictionary *opts = NULL;
+    xmlDoc *doc = NULL;
+    const char *base_url;
+
+    int close_in = 0;
+    int ret;
+    int64_t filesize;
+
+    base_url = av_dirname(strdup(url));
+    if (c->asset_locator_map == NULL) {
+        c->asset_locator_map = imf_asset_locator_map_alloc();
+        if (!c->asset_locator_map) {
+            av_log(s, AV_LOG_PANIC, "Unable to allocate asset map locator\n");
+            return AVERROR(ENOMEM);
+        }
+    }
+
+    av_log(s, AV_LOG_DEBUG, "Asset Map URL: %s\n", url);
+
+    if (!in) {
+        close_in = 1;
+
+        av_dict_copy(&opts, c->avio_opts, 0);
+        ret = avio_open2(&in, url, AVIO_FLAG_READ, c->interrupt_callback, &opts);
+        av_dict_free(&opts);
+        if (ret < 0)
+            return ret;
+    }
+
+    filesize = avio_size(in);
+    filesize = filesize > 0 ? filesize : DEFAULT_ASSETMAP_SIZE;
+
+    av_bprint_init(&buf, filesize + 1, AV_BPRINT_SIZE_UNLIMITED);
+
+    if ((ret = avio_read_to_bprint(in, &buf, MAX_BPRINT_READ_SIZE)) < 0 || !avio_feof(in) || (filesize = buf.len) == 0) {
+        av_log(s, AV_LOG_ERROR, "Unable to read to asset map '%s'\n", url);
+        if (ret == 0)
+            ret = AVERROR_INVALIDDATA;
+    } else {
+        LIBXML_TEST_VERSION
+
+        doc = xmlReadMemory(buf.str, filesize, url, NULL, 0);
+
+        ret = parse_imf_asset_map_from_xml_dom(s, doc, &c->asset_locator_map, base_url);
+        if (ret != 0) {
+            goto cleanup;
+        }
+
+        av_log(s, AV_LOG_DEBUG, "Found %d assets from %s\n", c->asset_locator_map->asset_count, url);
+
+    cleanup:
+        xmlFreeDoc(doc);
+    }
+    if (close_in) {
+        avio_close(in);
+    }
+    return ret;
+}
+
+static IMFAssetLocator *find_asset_map_locator(IMFAssetLocatorMap *asset_map, UUID uuid)
+{
+    IMFAssetLocator *asset_locator;
+    for (int i = 0; i < asset_map->asset_count; ++i) {
+        asset_locator = asset_map->assets[i];
+        if (memcmp(asset_map->assets[i]->uuid, uuid, 16) == 0) {
+            return asset_locator;
+        }
+    }
+    return NULL;
+}
+
+static int open_track_resource_context(AVFormatContext *s, IMFVirtualTrackResourcePlaybackCtx *track_resource)
+{
+    int ret = 0;
+    int64_t entry_point;
+
+    if (!track_resource->ctx) {
+        track_resource->ctx = avformat_alloc_context();
+        if (!track_resource->ctx) {
+            av_log(NULL, AV_LOG_PANIC, "Cannot allocate Track Resource Context\n");
+            return AVERROR(ENOMEM);
+        }
+    }
+
+    if (track_resource->ctx->iformat) {
+        av_log(s, AV_LOG_DEBUG, "Input context already opened for %s.\n", track_resource->locator->absolute_uri);
+        return ret;
+    }
+
+    ret = avformat_open_input(&track_resource->ctx, track_resource->locator->absolute_uri, NULL, NULL);
+    if (ret < 0) {
+        av_log(s, AV_LOG_ERROR, "Could not open %s input context: %s\n", track_resource->locator->absolute_uri, av_err2str(ret));
+        goto cleanup;
+    }
+
+    ret = avformat_find_stream_info(track_resource->ctx, NULL);
+    if (ret < 0) {
+        av_log(s, AV_LOG_ERROR, "Could not find %s stream information: %s\n", track_resource->locator->absolute_uri, av_err2str(ret));
+        goto cleanup;
+    }
+
+    // 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))) {
+        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, 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;
+
+    if (entry_point) {
+        av_log(s, AV_LOG_DEBUG, "Seek at resource %s entry point: %ld\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);
+        if (ret < 0) {
+            av_log(s, AV_LOG_ERROR, "Could not seek at %" PRId64 "on %s: %s\n", entry_point, track_resource->locator->absolute_uri, av_err2str(ret));
+            goto cleanup;
+        }
+    }
+
+    return ret;
+cleanup:
+    avformat_free_context(track_resource->ctx);
+    return ret;
+}
+
+static int open_track_file_resource(AVFormatContext *s, IMFTrackFileResource *track_file_resource, IMFVirtualTrackPlaybackCtx *track)
+{
+    IMFContext *c = s->priv_data;
+    IMFVirtualTrackResourcePlaybackCtx *track_resource;
+    IMFAssetLocator *asset_locator;
+
+    int ret;
+
+    if (!(asset_locator = find_asset_map_locator(c->asset_locator_map, track_file_resource->track_file_uuid))) {
+        av_log(s, AV_LOG_ERROR, "Could not find asset locator for UUID: " IMF_UUID_FORMAT "\n", UID_ARG(track_file_resource->track_file_uuid));
+        return AVERROR_INVALIDDATA;
+    }
+
+    av_log(s, AV_LOG_DEBUG, "Found locator for " IMF_UUID_FORMAT ": %s\n", UID_ARG(asset_locator->uuid), asset_locator->absolute_uri);
+
+    track_resource = av_mallocz(sizeof(IMFVirtualTrackResourcePlaybackCtx));
+    track_resource->locator = asset_locator;
+    track_resource->resource = track_file_resource;
+
+    if ((ret = open_track_resource_context(s, track_resource)) != 0) {
+        return ret;
+    }
+
+    for (int repetition = 0; repetition < track_file_resource->base.repeat_count; ++repetition) {
+        track->resources = av_realloc(track->resources, (track->resource_count + 1) * sizeof(IMFVirtualTrackResourcePlaybackCtx));
+        if (!track->resources) {
+            av_log(NULL, AV_LOG_PANIC, "Cannot allocate Virtual Track playback context\n");
+            return AVERROR(ENOMEM);
+        }
+        track->resources[track->resource_count++] = track_resource;
+        track->duration = av_add_q(track->duration, av_make_q((int)track_resource->resource->base.duration * track_resource->resource->base.edit_rate.den, track_resource->resource->base.edit_rate.num));
+    }
+
+    return ret;
+}
+
+static int open_virtual_track(AVFormatContext *s, IMFTrackFileVirtualTrack *virtual_track, int32_t track_index)
+{
+    IMFContext *c = s->priv_data;
+    IMFVirtualTrackPlaybackCtx *track;
+    int ret = 0;
+
+    track = av_mallocz(sizeof(IMFVirtualTrackPlaybackCtx));
+    if (!track) {
+        av_log(NULL, AV_LOG_PANIC, "Cannot allocate IMF Virtual Track Playback context\n");
+        return AVERROR(ENOMEM);
+    }
+    track->index = track_index;
+    track->duration = av_make_q(0, INT32_MAX);
+
+    for (int i = 0; i < virtual_track->resource_count; i++) {
+        av_log(s, AV_LOG_DEBUG, "Open stream from file " IMF_UUID_FORMAT ", stream %d\n", UID_ARG(virtual_track->resources[i].track_file_uuid), i);
+        if ((ret = open_track_file_resource(s, &virtual_track->resources[i], track)) != 0) {
+            av_log(s, AV_LOG_ERROR, "Could not open image track resource " IMF_UUID_FORMAT "\n", UID_ARG(virtual_track->resources[i].track_file_uuid));
+            return ret;
+        }
+    }
+
+    track->current_timestamp = av_make_q(0, track->duration.den);
+
+    c->tracks = av_realloc(c->tracks, (c->track_count + 1) * sizeof(IMFVirtualTrackPlaybackCtx));
+    if (!c->tracks) {
+        av_log(NULL, AV_LOG_PANIC, "Cannot allocate Virtual Track playback context\n");
+        return AVERROR(ENOMEM);
+    }
+    c->tracks[c->track_count++] = track;
+
+    return ret;
+}
+
+static void imf_virtual_track_playback_context_free(IMFVirtualTrackPlaybackCtx *track)
+{
+    if (!track) {
+        return;
+    }
+
+    for (int i = 0; i < track->resource_count; ++i) {
+        if (!track->resources[i]) {
+            continue;
+        }
+
+        if (track->resources[i]->ctx && track->resources[i]->ctx->iformat) {
+            avformat_free_context(track->resources[i]->ctx);
+            track->resources[i]->ctx = NULL;
+        }
+    }
+}
+
+static int set_context_streams_from_tracks(AVFormatContext *s)
+{
+    IMFContext *c = s->priv_data;
+
+    AVStream *asset_stream;
+    AVStream *first_resource_stream;
+
+    int ret = 0;
+
+    for (int i = 0; i < c->track_count; ++i) {
+        // Open the first resource of the track to get stream information
+        first_resource_stream = c->tracks[i]->resources[0]->ctx->streams[0];
+
+        av_log(s, AV_LOG_DEBUG, "Open the first resource of track %d\n", c->tracks[i]->index);
+
+        // Copy stream information
+        asset_stream = avformat_new_stream(s, NULL);
+        asset_stream->id = i;
+        if ((ret = avcodec_parameters_copy(asset_stream->codecpar, first_resource_stream->codecpar)) < 0) {
+            av_log(s, AV_LOG_ERROR, "Could not copy stream parameters\n");
+            break;
+        }
+        avpriv_set_pts_info(asset_stream, first_resource_stream->pts_wrap_bits, first_resource_stream->time_base.num, first_resource_stream->time_base.den);
+        asset_stream->duration = (int64_t)av_q2d(av_mul_q(c->tracks[i]->duration, av_inv_q(asset_stream->time_base)));
+    }
+
+    return ret;
+}
+
+static int open_cpl_tracks(AVFormatContext *s)
+{
+    IMFContext *c = s->priv_data;
+    int32_t track_index = 0;
+    int ret;
+
+    if (c->cpl->main_image_2d_track) {
+        if ((ret = open_virtual_track(s, c->cpl->main_image_2d_track, track_index++)) != 0) {
+            av_log(s, AV_LOG_ERROR, "Could not open image track " IMF_UUID_FORMAT "\n", UID_ARG(c->cpl->main_image_2d_track->base.id_uuid));
+            return ret;
+        }
+    }
+
+    for (int audio_track_index = 0; audio_track_index < c->cpl->main_audio_track_count; ++audio_track_index) {
+        if ((ret = open_virtual_track(s, &c->cpl->main_audio_tracks[audio_track_index], track_index++)) != 0) {
+            av_log(s, AV_LOG_ERROR, "Could not open audio track " IMF_UUID_FORMAT "\n", UID_ARG(c->cpl->main_audio_tracks[audio_track_index].base.id_uuid));
+            return ret;
+        }
+    }
+
+    return set_context_streams_from_tracks(s);
+}
+
+static int imf_close(AVFormatContext *s);
+
+static int imf_read_header(AVFormatContext *s)
+{
+    IMFContext *c = s->priv_data;
+    char *asset_map_path;
+    int ret;
+
+    c->base_url = av_dirname(av_strdup(s->url));
+
+    av_log(s, AV_LOG_DEBUG, "start parsing IMF CPL: %s\n", s->url);
+
+    if ((ret = parse_imf_cpl(s->pb, &c->cpl)) < 0)
+        goto fail;
+
+    av_log(s, AV_LOG_DEBUG, "parsed IMF CPL: " IMF_UUID_FORMAT "\n", UID_ARG(c->cpl->id_uuid));
+
+    if (!c->asset_map_paths) {
+        c->asset_map_paths = av_append_path_component(c->base_url, "ASSETMAP.xml");
+    }
+
+    // Parse each asset map XML file
+    asset_map_path = strtok(c->asset_map_paths, ",");
+    while (asset_map_path != NULL) {
+        av_log(s, AV_LOG_DEBUG, "start parsing IMF Asset Map: %s\n", asset_map_path);
+
+        if ((ret = parse_assetmap(s, asset_map_path, NULL)) < 0)
+            goto fail;
+
+        asset_map_path = strtok(NULL, ",");
+    }
+
+    av_log(s, AV_LOG_DEBUG, "parsed IMF Asset Maps\n");
+
+    if ((ret = open_cpl_tracks(s)) != 0) {
+        goto fail;
+    }
+
+    av_log(s, AV_LOG_DEBUG, "parsed IMF package\n");
+    return ret;
+
+fail:
+    imf_close(s);
+    return ret;
+}
+
+static IMFVirtualTrackPlaybackCtx *get_next_track_with_minimum_timestamp(AVFormatContext *s)
+{
+    IMFContext *c = s->priv_data;
+    IMFVirtualTrackPlaybackCtx *track;
+
+    AVRational minimum_timestamp = av_make_q(INT32_MAX, 1);
+    for (int i = 0; i < c->track_count; ++i) {
+        av_log(s, AV_LOG_DEBUG, "Compare track %d timestamp " IMF_AVRATIONAL_FORMAT " to minimum " IMF_AVRATIONAL_FORMAT " (over duration: " IMF_AVRATIONAL_FORMAT ")\n", i, IMF_AVRATIONAL_ARG(c->tracks[i]->current_timestamp), IMF_AVRATIONAL_ARG(minimum_timestamp), IMF_AVRATIONAL_ARG(c->tracks[i]->duration));
+        if (av_cmp_q(c->tracks[i]->current_timestamp, minimum_timestamp) < 0) {
+            track = c->tracks[i];
+            minimum_timestamp = track->current_timestamp;
+        }
+    }
+
+    av_log(s, AV_LOG_DEBUG, "Found next track to read: %d (timestamp: %lf / %lf)\n", track->index, av_q2d(track->current_timestamp), av_q2d(minimum_timestamp));
+    return track;
+}
+
+static IMFVirtualTrackResourcePlaybackCtx *get_resource_context_for_timestamp(AVFormatContext *s, IMFVirtualTrackPlaybackCtx *track)
+{
+    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);
+
+    av_log(s, AV_LOG_DEBUG, "Looking for track %d resource for timestamp = %lf / %lf\n", track->index, av_q2d(track->current_timestamp), av_q2d(track->duration));
+    for (int 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) {
+            av_log(s, AV_LOG_DEBUG, "Found resource %d in track %d to read for timestamp %lf (on cumulated=%lf): entry=%ld, duration=%lu, editrate=" IMF_AVRATIONAL_FORMAT " | edit_unit_duration=%lf\n", 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, IMF_AVRATIONAL_ARG(track->resources[i]->resource->base.edit_rate), av_q2d(edit_unit_duration));
+
+            if (track->current_resource_index != i) {
+                av_log(s, AV_LOG_DEBUG, "Switch resource on track %d: re-open context\n", track->index);
+                if (track->resources[track->current_resource_index] != NULL) {
+                    avformat_close_input(&track->resources[track->current_resource_index]->ctx);
+                }
+                if (open_track_resource_context(s, track->resources[i]) != 0) {
+                    return NULL;
+                }
+                track->current_resource_index = i;
+            }
+            return track->resources[track->current_resource_index];
+        }
+    }
+    return NULL;
+}
+
+static int ff_imf_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    IMFContext *c = s->priv_data;
+
+    IMFVirtualTrackResourcePlaybackCtx *resource_to_read = NULL;
+    AVRational edit_unit_duration;
+    int ret = 0;
+
+    IMFVirtualTrackPlaybackCtx *track_to_read = get_next_track_with_minimum_timestamp(s);
+    FFStream *track_to_read_stream_internal;
+
+    if (av_cmp_q(track_to_read->current_timestamp, track_to_read->duration) == 0) {
+        return AVERROR_EOF;
+    }
+
+    resource_to_read = get_resource_context_for_timestamp(s, track_to_read);
+
+    if (!resource_to_read) {
+        edit_unit_duration = av_inv_q(track_to_read->resources[track_to_read->current_resource_index]->resource->base.edit_rate);
+        if (av_cmp_q(av_add_q(track_to_read->current_timestamp, edit_unit_duration), track_to_read->duration) > 0) {
+            return AVERROR_EOF;
+        }
+
+        av_log(s, AV_LOG_ERROR, "Could not find IMF track resource to read\n");
+        return AVERROR_STREAM_NOT_FOUND;
+    }
+
+    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_to_read_stream_internal = ffstream(s->streams[track_to_read->index]);
+        if (ret >= 0) {
+            // Update packet info from track
+            if (pkt->dts < track_to_read_stream_internal->cur_dts && track_to_read->last_pts > 0) {
+                pkt->dts = track_to_read_stream_internal->cur_dts;
+            }
+
+            pkt->pts = track_to_read->last_pts;
+            pkt->dts = pkt->dts - (int64_t)track_to_read->resources[track_to_read->current_resource_index]->resource->base.entry_point;
+            pkt->stream_index = track_to_read->index;
+
+            // Update track cursors
+            track_to_read->current_timestamp = av_add_q(track_to_read->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_to_read->last_pts += pkt->duration;
+
+            return 0;
+        } else if (ret != AVERROR_EOF) {
+            av_log(s, AV_LOG_ERROR, "Could not get packet from track %d: %s\n", track_to_read->index, av_err2str(ret));
+            return ret;
+        }
+    }
+
+    return AVERROR_EOF;
+}
+
+static int imf_close(AVFormatContext *s)
+{
+    IMFContext *c = s->priv_data;
+
+    av_log(s, AV_LOG_DEBUG, "Close IMF package\n");
+    av_dict_free(&c->avio_opts);
+    av_freep(&c->base_url);
+    imf_asset_locator_map_free(c->asset_locator_map);
+    imf_cpl_free(c->cpl);
+
+    for (int i = 0; i < c->track_count; ++i) {
+        imf_virtual_track_playback_context_free(c->tracks[i]);
+    }
+
+    return 0;
+}
+
+static const AVOption imf_options[] = {
+    {"assetmaps", "IMF CPL-related asset map comma-separated absolute paths. If not specified, the CPL sibling `ASSETMAP.xml` file is used.", offsetof(IMFContext, asset_map_paths), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, AV_OPT_FLAG_DECODING_PARAM},
+    {NULL}};
+
+static const AVClass imf_class = {
+    .class_name = "imf",
+    .item_name = av_default_item_name,
+    .option = imf_options,
+    .version = LIBAVUTIL_VERSION_INT,
+};
+
+const AVInputFormat ff_imf_demuxer = {
+    .name = "imf",
+    .long_name = NULL_IF_CONFIG_SMALL("IMF (Interoperable Master Format)"),
+    .priv_class = &imf_class,
+    .priv_data_size = sizeof(IMFContext),
+    .read_header = imf_read_header,
+    .read_packet = ff_imf_read_packet,
+    .read_close = imf_close,
+    .extensions = "xml",
+    .mime_type = "application/xml,text/xml",
+};
-- 
2.17.1



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